SN250QT

SN250 Single-chip ZigBee® 802.15.4 solution Features ■ Integrated 2.4GHz, IEEE 802.15.4-compliant transceiver: – Robust RX filtering allows co-existence with IEEE 802.11g and Bluetooth devices – − 97 dBm RX sensitivity (1% PER, 20 byte packet) – + 3dBm nominal output power – Increased radio performance mode (boost mode) gives −98 dBm sensitivity and +5dBm transmit power – Integrated VCO and loop filter ■ Integrated memory: – 128 Kbytes of Flash – 5 Kbytes of SRAM ■ Configurable memory protection scheme ■ Two sleep modes: – Processor idle – Deep sleep -1.0 µA (1.5 µA with optional 32.768-kHz oscillator enabled) ■ Seventeen GPIO pins with alternate functions ■ Two Serial Controllers with DMA – SC1: I2C master, SPI master, UART – SC2: I2C master, SPI master/slave ■ Integrated IEEE 802.15.4 PHY and lower MAC with DMA ■ ■ Integrated hardware support for Packet Trace Interface for InSight Development Environment Two 16-bit general-purpose timers; one 16-bit sleep timer ■ Watchdog timer and power-on-reset circuitry ■ Provides integrated RC oscillator for low power operation ■ Non-intrusive debug interface (SIF) ■ Integrated AES encryption accelerator ■ Supports optional 32.768-kHz crystal oscillator for higher accuracy needs ■ Integrated ADC module first-order, sigma-delta converter with 12-bit resolution ■ 16-bit XAP2b microprocessor ■ Integrated 1.8V voltage regulator October 2007 Rev 3 1/130 www.st.com 1 Contents SN250 Contents 1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Top-level functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6 5.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3 Environmental characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.4 DC electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.5 RF electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.5.2 Transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.5.3 Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Functional description—system modules . . . . . . . . . . . . . . . . . . . . . . 20 6.1 6.2 2/130 5.5.1 Receive (RX) path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.1.1 RX baseband . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.1.2 RSSI and CCA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Transmit (TX) path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.2.1 TX baseband . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.2.2 TX_ACTIVE signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.3 Integrated MAC module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.4 Packet Trace Interface (PTI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6.5 XAP2b microprocessor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6.6 Embedded memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.6.1 Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.6.2 Simulated EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.6.3 Flash Information Area (FIA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.6.4 RAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.6.5 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 SN250 7 Contents 6.7 Encryption accelerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.8 Reset detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 6.9 Power-on-Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 6.10 Clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 6.10.1 High-frequency crystal oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 6.10.2 Low-frequency oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 6.10.3 Internal RC oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6.11 Random number generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6.12 Watchdog timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6.13 Sleep timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6.14 Power management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Functional description—application modules . . . . . . . . . . . . . . . . . . . 31 7.1 GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 7.1.1 7.2 7.3 7.4 7.5 Serial controller SC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 7.2.1 UART mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2.2 SPI master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 7.2.3 I2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 7.2.4 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Serial controller SC2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 7.3.1 SPI modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 7.3.2 I2C Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 7.3.3 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 General purpose timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.4.1 Clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.4.2 Timer functionality (counting) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.4.3 Timer functionality (output compare) . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 7.4.4 Timer functionality (input capture) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 7.4.5 Timer interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 7.4.6 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 ADC module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 7.5.1 7.6 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Event manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 7.6.1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 3/130 Contents SN250 7.7 Integrated voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 8 SIF module programming and debug interface . . . . . . . . . . . . . . . . . 117 9 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 10 Mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 11 Register address table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 12 Abbreviations and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 14 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 4/130 SN250 1 General description General description The SN250 is a single-chip solution that integrates a 2.4GHz, IEEE 802.15.4-compliant transceiver with a 16-bit XAP2b microprocessor. It contains integrated Flash and RAM memory and peripherals of use to designers of ZigBee®-based applications. The transceiver utilizes an efficient architecture that exceeds the dynamic range requirements imposed by the IEEE 802.15.4-2003 standard by over 15dB. The integrated receive channel filtering allows for co-existence with other communication standards in the 2.4GHz spectrum such as IEEE 802.11g and Bluetooth. The integrated regulator, VCO, loop filter, and power amplifier keep the external component count low. An optional high performance radio mode (boost mode) is software selectable to boost dynamic range by a further 3dB. The XAP2b microprocessor is a power-optimized core integrated in the SN250. It supports two different modes of operation—System Mode and Application Mode. The ZNet stack runs in System Mode with full access to all areas of the chip. Application code runs in Application Mode with limited access to the SN250 resources; this allows for the scheduling of events by the application developer while preventing modification of restricted areas of memory and registers. This architecture results in increased stability and reliability of deployed solutions. The SN250 has 128KB of embedded Flash memory and 5KB of integrated RAM for data and program storage. The SN250 software stack employs an effective wear-leveling algorithm in order to optimize the lifetime of the embedded Flash. To maintain the strict timing requirements imposed by ZigBee and the IEEE 802.15.4-2003 standard, the SN250 integrates a number of MAC functions into the hardware. The MAC hardware handles automatic ACK transmission and reception, automatic backoff delay, and clear channel assessment for transmission, as well as automatic filtering of received packets. In addition, the SN250 allows for true MAC level debugging by integrating the Packet Trace Interface. To support user-defined applications, a number of peripherals such as GPIO, UART, SPI, I2C, ADC, and general-purpose timers are integrated. Also, an integrated voltage regulator, power-on-reset circuitry, sleep timer, and low-power sleep modes are available. The deep sleep mode draws less than 1μA, allowing products to achieve long battery life. Finally, the SN250 utilizes the non-intrusive SIF module for powerful software debugging and programming of the XAP2b microcontroller. Target applications for the SN250 include: ● Building automation and control ● Home automation and control ● Home entertainment control ● Asset tracking The SN250 is purchased with ZNet, a ZigBee-compliant software stack developed by Ember Corporation, providing a ZigBee profile-ready, platform-compliant solution.This technical datasheet details the SN250 features available to customers using it with the ZNet stack. 5/130 Order codes 2 SN250 Order codes Part Number 3 Temperature Range Package Packing Marking SN250Q -40 to +85°C QFN48 Tray SN250 SN250QT -40 to +85°C QFN48 Tape & Reel SN250 Pin assignment Figure 1. SN250 pin assignment Refer to Table 17 and Table 18 for selecting alternate pin functions. 6/130 SN250 Table 1. Pin assignment Pin descriptions Pin # Signal Direction Description 1 VDD_24MHZ Power 1.8V high-frequency oscillator supply 2 VDD_VCO Power 1.8V VCO supply 3 RF_P I/O Differential (with RF_N) receiver input/transmitter output 4 RF_N I/O Differential (with RF_P) receiver input/transmitter output 5 VDD_RF Power 1.8V RF supply (LNA and PA) 6 RF_TX_ALT_P O Differential (with RF_TX_ALT_N) transmitter output (optional) 7 RF_TX_ALT_N O Differential (with RF_TX_ALT_P) transmitter output (optional) 8 VDD_IF Power 1.8V IF supply (mixers and filters) 9 BIAS_R I Bias setting resistor 10 VDD_PADSA Power Analog pad supply (1.8V) 11 TX_ACTIVE O Logic-level control for external RX/TX switch 12 VDD_PADSA Power Analog pad supply (1.8V) 13 nRESET I Active low chip reset (internal pull-up) 14 OSC32B I/O 32.768kHz crystal oscillator or left open when using external clock on OSC32A 15 OSC32A I/O 32.768kHz crystal oscillator or digital clock input 16 VREG_OUT Power Regulator output (1.8V) 17 VDD_PADS Power Pads supply (2.1–3.6V) 18 VDD_CORE Power 1.8V digital core supply GPIO11 I/O Digital I/O (enable GPIO11 with GPIO_CFG[7:4]) nCTS I UART CTS handshake of Serial Controller SC1 (enable SC1-4A with GPIO_CFG[7:4], select UART with SC1_MODE) MCLK O SPI master clock of Serial Controller SC1 (enable SC1-3M with GPIO_CFG[7:4], select SPI with SC1_MODE, enable master with SC1_SPICFG[4]) TMR2IA.1 I Capture Input A of Timer 2 (enable CAP2-0 with GPIO_CFG[7:4]) GPIO12 I/O Digital I/O (enable GPIO12 with GPIO_CFG[7:4]) nRTS O UART RTS handshake of Serial Controller SC1 (enable SC1-4A with GPIO_CFG[7:4], select UART with SC1_MODE) TMR2IB.1 I Capture Input B for Timer 2 (enable CAP2-0 with GPIO_CFG[7:4]) 19 20 7/130 Pin assignment Table 1. Pin # SN250 Pin descriptions (continued) Signal Direction Description GPIO0 I/O Digital I/O (enable GPIO0 with GPIO_CFG[7:4]) MOSI O SPI master data out of Serial Controller SC2 (enable SC2-3M with GPIO_CFG[7:4], select SPI with SC2_MODE, enable master with SC2_SPICFG[4]) MOSI I SPI slave data in of Serial Controller SC2 (enable SC2-4S with GPIO_CFG[7:4], select SPI with SC2_MODE, enable slave with SC2_SPICFG[4]) TMR1IA.1 I Capture Input A of Timer 1 (enable CAP1-0 with GPIO_CFG[7:4]) GPIO1 I/O Digital I/O (enable GPIO1 with GPIO_CFG[7:4]) MISO I SPI master data in of Serial Controller SC2 (enable SC2-3M with GPIO_CFG[7:4], select SPI with SC2_MODE, enable master with SC2_SPICFG[4]) MISO O SPI slave data out of Serial Controller SC2 (enable SC2-4S with GPIO_CFG[7:4], select SPI with SC2_MODE, enable slave with SC2_SPICFG[4]) SDA I/O I2C data of Serial Controller SC2 (enable SC2-2 with GPIO_CFG[7:4], select I2C with SC2_MODE) TMR2IA.2 I Capture Input A of Timer 2 (enable CAP2-1 with GPIO_CFG[7:4]) VDD_PADS Power Pads supply (2.1–3.6V) GPIO2 I/O Digital I/O (enable GPIO2 with GPIO_CFG[7:4]) MSCLK O SPI master clock of Serial Controller SC2 (enable SC2-3M with GPIO_CFG[7:4], select SPI with SC2_MODE, enable master with SC2_SPICFG[4]) MSCLK I SPI slave clock of Serial Controller SC2 (enable SC2-4S with GPIO_CFG[7:4], select SPI with SC2_MODE, enable slave with SC2_SPICFG[4]) nSSEL I/O I2C clock of Serial Controller SC2 (enable SC2-2 with GPIO_CFG[7:4], select I2C with SC2_MODE) TMR2IB.2 I Capture Input B of Timer 2 (enable CAP2-1 with GPIO_CFG[7:4]) 21 22 23 24 8/130 SN250 Table 1. Pin # 25 26 27 28 29 30 Pin assignment Pin descriptions (continued) Signal Direction Description GPIO3 I/O Digital I/O (enable GPIO3 with GPIO_CFG[7:4]) nSSEL I SPI slave select of Serial Controller SC2 (enable SC2-4S with GPIO_CFG[7:4], select SPI with SC2_MODE, enable slave with SC2_SPICFG[4]) TMR1IB.1 I Capture Input B of Timer 1 (enable CAP1-0 with GPIO_CFG[7:4]) GPIO4 I/O Digital I/O (enable GPIO4 with GPIO_CFG[12] and GPIO_CFG[8]) ADC0 Analog ADC Input 0 (enable ADC0 with GPIO_CFG[12] and GPIO_CFG[8]) PTI_EN O Frame signal of Packet Trace Interface (PTI) (enable PTI with GPIO_CFG[12]) GPIO5 I/O Digital I/O (enable GPIO5 with GPIO_CFG[12] and GPIO_CFG[9]) ADC1 Analog ADC Input 1 (enable ADC1 with GPIO_CFG[12] and GPIO_CFG[9]) PTI_DATA O Data signal of Packet Trace Interface (PTI) (enable PTI with GPIO_CFG[12]) VDD_PADS Power Pads supply (2.1–3.6V) GPIO6 I/O Digital I/O (enable GPIO6 with GPIO_CFG[10]) ADC2 Analog ADC Input 2 (enable ADC2 with GPIO_CFG[10]) TMR2CLK I External clock input of Timer 2 TMR1ENMSK I External enable mask of Timer 1 GPIO7 I/O Digital I/O (enable GPIO7 with GPIO_CFG[13] and GPIO_CFG[11]) ADC3 Analog ADC Input 3 (enable ADC3 with GPIO_CFG[13] and GPIO_CFG[11]) REG_EN O External regulator open collector output (enable REG_EN with GPIO_CFG[13]) GPIO8 I/O Digital I/O (enable GPIO8 with GPIO_CFG[14]) VREF_OUT Analog ADC reference output (enable VREF_OUT with GPIO_CFG[14]) TMR1CLK I External clock input of Timer 1 TMR2ENMSK I External enable mask of Timer 2 IRQA I External interrupt source A 31 9/130 Pin assignment Table 1. Pin # SN250 Pin descriptions (continued) Signal Direction Description GPIO9 I/O Digital I/O (enable GPIO9 with GPIO_CFG[7:4]) TXD O UART transmit data of Serial Controller SC1 (enable SC1-4A or SC1-2 with GPIO_CFG[7:4], select UART with SC1_MODE) MO O SPI master data out of Serial Controller SC1 (enable SC1-3M with GPIO_CFG[7:4], select SPI with SC1_MODE, enable master with SC1_SPICFG[4]) MSDA I/O I2C data of Serial Controller SC1 (enable SC1-2 with GPIO_CFG[7:4], select I2C with SC1_MODE) TMR1IA.2 I Capture Input A of Timer 1 (enable CAP1-1 or CAP1-1h with GPIO_CFG[7:4]) GPIO10 I/O Digital I/O (enable GPIO10 with GPIO_CFG[7:4]) RXD I UART receive data of Serial Controller SC1 (enable SC1-4A or SC1-2 with GPIO_CFG[7:4], select UART with SC1_MODE) MI I SPI master data in of Serial Controller SC1 (enable SC1-3M with GPIO_CFG[7:4], select SPI with SC1_MODE, enable master with SC1_SPICFG[4]) MSCL I/O I2C clock of Serial Controller SC1 (enable SC1-2 with GPIO_CFG[7:4], select I2C with SC1_MODE) TMR1IB.2 I Capture Input B of Timer 2 (enable CAP1-1 with GPIO_CFG[7:4]) 34 SIF_CLK I Serial interface, clock (internal pull-down) 35 SIF_MISO O Serial interface, master in/slave out 36 SIF_MOSI I Serial interface, master out/slave in 37 nSIF_LOADB I/O Serial interface, load strobe (open-collector with internal pull-up) 38 GND Power Ground supply 39 VDD_FLASH Power 1.8V Flash memory supply GPIO16 I/O Digital I/O (enable GPIO16 with GPIO_CFG[3]) TMR1OB O Waveform Output B of Timer 1 (enable TMR1OB with GPIO_CFG[3]) TMR2IB.3 I Capture Input B of Timer 2 (enable CAP2-2 with GPIO_CFG[7:4]) IRQD I External interrupt source D 32 33 40 10/130 SN250 Table 1. Pin # Pin assignment Pin descriptions (continued) Signal Direction Description GPIO15 I/O Digital I/O (enable GPIO15 with GPIO_CFG[2]) TMR1OA O Waveform Output A of Timer 1 (enable TMR1OA with GPIO_CFG[2]) TMR2IA.3 I Capture Input A of Timer 2 (enable CAP2-2 with GPIO_CFG[7:4]) IRQC I External interrupt source C GPIO14 I/O Digital I/O (enable GPIO14 with GPIO_CFG[1]) TMR2OB O Waveform Output B of Timer 2 (enable TMR2OB with GPIO_CFG[1]) TMR1IB.3 I Capture Input B of Timer 1 (enable CAP1-2 with GPIO_CFG[7:4]) IRQB I External interrupt source B GPIO13 I/O Digital I/O (enable GPIO13 with GPIO_CFG[0]) TMR2OA O Waveform Output A of Timer 2 (enable TMR2OA with GPIO_CFG[0]) TMR1IA.3 I Capture Input A of Timer 1 (enable CAP1-2 or CAP1-2h with GPIO_CFG[7:4]) 44 VDD_CORE Power 1.8V digital core supply 45 VDD_PRE Power 1.8V prescaler supply 46 VDD_SYNTH Power 1.8V synthesizer supply 47 OSCB I/O 24MHz crystal oscillator or left open when using external clock input on OSCA 48 OSCA I/O 24MHz crystal oscillator or external clock input 49 GND Ground Ground supply pad in the bottom center of the package forms Pin 49 (see the SN250 Reference Design for PCB considerations) 41 42 43 11/130 Top-level functional description 4 SN250 Top-level functional description Figure 2 shows a detailed block diagram of the SN250. Figure 2. SN250 block diagram The radio receiver is a low-IF, super-heterodyne receiver. It utilizes differential signal paths to minimize noise interference, and its architecture has been chosen to optimize coexistence with other devices within the 2.4GHz band (namely, IEEE 802.11g and Bluetooth). After amplification and mixing, the signal is filtered and combined prior to being sampled by an ADC. The digital receiver implements a coherent demodulator to generate a chip stream for the hardware-based MAC. In addition, the digital receiver contains the analog radio calibration routines and control of the gain within the receiver path. The radio transmitter utilizes an efficient architecture in which the data stream directly modulates the VCO. An integrated PA boosts the output power. The calibration of the TX path as well as the output power is controlled by digital logic. If the SN250 is to be used with an external PA, the TX_ACTIVE signal should be used to control the timing of the external switching logic. The integrated 4.8 GHz VCO and loop filter minimize off-chip circuitry. Only a 24MHz crystal with its loading capacitors is required to properly establish the PLL reference signal. The MAC interfaces the data memory to the RX and TX baseband modules. The MAC provides hardware-based IEEE 802.15.4 packet-level filtering. It supplies an accurate symbol time base that minimizes the synchronization effort of the software stack and meets 12/130 SN250 Top-level functional description the protocol timing requirements. In addition, it provides timer and synchronization assistance for the IEEE 802.15.4 CSMA-CA algorithm. The SN250 integrates hardware support for a Packet Trace module, which allows robust packet-based debug. This element is a critical component of InSight Desktop, the software IDE developed by Ember Corporation, providing advanced network debug capability when coupled with the InSight Adapter. The SN250 integrates a 16-bit XAP2b microprocessor developed by Cambridge Consultants Ltd. This power-efficient, industry-proven core provides the appropriate level of processing power to meet the needs of ZigBee applications. In addition, 128KB of Flash and 5KB of SRAM comprise the program and data memory elements, respectively. The SN250 employs a configurable memory protection scheme usually found on larger microcontrollers. In addition, the SIF module provides a non-intrusive programming and debug interface allowing for real-time application debugging. The SN250 contains 17 GPIO pins shared with other peripheral (or alternate) functions. Flexible routing within the SN250 lets external devices utilize the alternate functions on a variety of different GPIOs. The integrated Serial Controller SC1 can be configured for SPI (master-only), I2C (master-only), or UART functionality, and the Serial Controller SC2 can be configured for SPI (master or slave) or I2C (master-only) operation. The SN250 has an ADC integrated which can sample analog signals from four GPIO pins single-ended or differentially. In addition, the unregulated voltage supply VDD_PADS, regulated supply VDD_PADSA, voltage reference VREF, and GND can be sampled. The integrated voltage reference VREF for the ADC can be made available to external circuitry. The integrated voltage regulator generates a regulated 1.8V reference voltage from an unregulated supply voltage. This voltage is decoupled and routed externally to supply the 1.8V to the core logic. In addition, an integrated POR module allows for the proper cold start of the SN250. The SN250 contains one high-frequency (24MHz) crystal oscillator and, for low-power operation, a second low-frequency oscillator (either an internal 10kHz RC oscillator or an external 32.768kHz crystal oscillator). The SN250 contains two power domains. The always-powered High Voltage Supply is used for powering the GPIO pads and critical chip functions. The rest of the chip is powered by a regulated Low Voltage Supply which can be disabled during deep sleep to reduce the power consumption. 13/130 Electrical characteristics SN250 5 Electrical characteristics 5.1 Absolute maximum ratings Table 2 lists the absolute maximum ratings for the SN250. Table 2. Absolute maximum ratings Parameter 5.2 Test Conditions Min. Max. Unit Regulator voltage (VDD_PADS) − 0.3 3.6 V Core voltage (VDD_24MHz, VDD_VCO, VDD_RF, VDD_IF, VDD_PADSA, VDD_FLASH, VDD_PRE, VDD_SYNTH, VDD_CORE) − 0.3 2.0 V Voltage on RF_P,N; RF_TX_ALT_P,N − 0.3 3.6 V Voltage on any GPIO[16:0], SIF_CLK, SIF_MISO, SIF_MOSI, SIF_LOADB, OSC32A, OSC32B, RSTB, VREG_OUT − 0.3 VDD_PADS + 0.3 V Voltage on TX_ACTIVE, BIAS_R, OSCA, OSCB − 0.3 VDD_CORE + 0.3 V Storage temperature − 40 + 140 °C Recommended operating conditions Table 3 lists the rated operating conditions of the SN250. . Table 3. Operating conditions Parameter 14/130 Test Conditions Min. Regulator input voltage (VDD_PADS) 2.1 Core input voltage (VDD_24MHZ, VDD_VCO, VDD_RF, VDD_IF, VDD_PADSA, VDD_FLASH, VDD_PRE, VDD_SYNTH, VDD_CORE) 1.7 Temperature range -40 Typ. 1.8 Max. Unit 3.6 V 1.9 V + 85 °C SN250 5.3 Electrical characteristics Environmental characteristics Table 4 lists the environmental characteristics of the SN250. Table 4. Environmental characteristics Parameter Test Conditions Min. On any Pin ESD (charged device model) ESD (charged device model) ESD (human body model) Max. Unit −2 +2 kV Non-RF Pins − 400 + 400 V RF Pins − 225 + 225 V Max. Unit 3.6 V 1.9 V Moisture Sensitivity Level (MSL1) 5.4 Typ. TBD DC electrical characteristics Table 5 lists the DC electrical characteristics of the SN250. Table 5. DC characteristics Parameter Test Conditions Regulator input voltage (VDD_PADS) Power supply range (VDD_CORE) Min. Typ. 2.1 Regulator output or external input 1.7 1.8 Deep Sleep Current Quiescent current, including internal RC oscillator At 25° C. 1.0 μA Quiescent current, including 32.768kHz oscillator At 25° C. 1.5 μA RX Current Radio receiver, MAC, and baseband (boost mode) 29.0 mA Radio receiver, MAC, and baseband 27.0 mA CPU, RAM, and Flash memory At 25° C and 1.8V core 8.5 mA Total RX current ( = IRadio receiver, MAC and baseband, CPU + IRAM, and Flash memory) At 25° C, VDD_PADS=3.0V 35.5 mA At max. TX power (+ 5dBm typical) 33.0 mA TX Current Radio transmitter, MAC, and baseband (boost mode) 15/130 Electrical characteristics Table 5. SN250 DC characteristics (continued) Parameter Test Conditions Radio transmitter, MAC, and baseband CPU, RAM, and Flash memory Min. Typ. Max. Unit At max. TX power (+ 3dBm typical) 27.0 mA At 0 dBm typical 24.3 mA At min. TX power (− 32dBm typical) 19.5 mA At 25° C, VDD_PADS = 3.0V 8.5 mA 35.5 mA Total TX current ( = IRadio transmitter, MAC and baseband, At 25° C and 1.8V core; max. power out CPU + IRAM, and Flash memory ) Table 6 contains the digital I/O specifications for the SN250. The digital I/O power (named VDD_PADS) comes from three dedicated pins (Pins 17, 23, and 28). The voltage applied to these pins sets the I/O voltage. Table 6. Digital I/O specifications Parameter Name Voltage supply VDD_PADS Input voltage for logic 0 Min. Max. Unit 2.1 3.6 V VIL 0 0.2 x VDD_PADS V Input voltage for logic 1 VIH 0.8 x VDD_PADS VDD_PADS V Input current for logic 0 IIL − 0.5 μA Input current for logic 1 IIH 0.5 μA Input pull-up resistor value RIPU 30 kΩ Input pull-down resistor value RIPD 30 kΩ Output voltage for logic 0 VOL 0 0.18 x VDD_PADS V Output voltage for logic 1 VOH 0.82 x VDD_PADS VDD_PADS V Output source current (standard current pad) IOHS 4 mA Output sink current (standard current pad) IOLS 4 mA Output source current (high IOHH current pad: GPIO[16:13]) 8 mA Output sink current (high current pad: GPIO[16:13]) 8 mA 40 mA 0.8 ∗ VDD_PADS V IOLH Total output current (for I/O IOH + IOL Pads) Input voltage threshold for OSC32A 16/130 0.2 Typ. SN250 Electrical characteristics Table 6. Digital I/O specifications Parameter Input voltage threshold for OSCA Output voltage level (TX_ACTIVE) Output source current (TX_ACTIVE) Name Min. Typ. Max. Unit 0.2 0.8 ∗ VDD_CORE 0.18 ∗ VDD_CORE 0.82 ∗ VDD_CORE V 1 mA 17/130 Electrical characteristics SN250 5.5 RF electrical characteristics 5.5.1 Receive Table 7 lists the key parameters of the integrated IEEE 802.15.4 receiver on the SN250. . Table 7. Receive characteristics Parameter Test Conditions Frequency range Min. 2400 Max. Unit 2500 MHz Sensitivity (boost mode) 1% PER, 20byte packet defined by IEEE 802.15.4 − 93 − 98 dBm Sensitivity 1% PER, 20byte packet defined by IEEE 802.15.4 − 92 − 97 dBm High-side adjacent channel rejection IEEE 802.15.4 signal at − 82dBm 35 dB Low-side adjacent channel rejection IEEE 802.15.4 signal at − 82dBm 35 dB 2nd high-side adjacent channel rejection IEEE 802.15.4 signal at − 82dBm 40 dB 2nd low-side adjacent channel rejection IEEE 802.15.4 signal at − 82dBm 40 dB Channel rejection for all other channels IEEE 802.15.4 signal at − 82dBm 40 dB 802.11g rejection centered at + 12MHz or − 13MHz IEEE 802.15.4 signal at − 82dBm 40 dB Maximum input signal level for correct operation (low gain) 0 Image suppression Co-channel rejection IEEE 802.15.4 signal at − 82dBm dBm 30 dB −6 dBc Relative frequency error (2x40 ppm required by IEEE 802.15.4) − 120 + 120 ppm Relative timing error (2x40 ppm required by IEEE 802.15.4) − 120 + 120 ppm Linear RSSI range 18/130 Typ. 40 dB SN250 5.5.2 Electrical characteristics Transmit Table 8 lists the key parameters of the integrated IEEE 802.15.4 transmitter on the SN250. Table 8. Transmit characteristics Parameter Test Conditions Maximum output power (boost mode) At highest power setting Maximum output power At highest power setting Minimum output power Error vector magnitude Min. Max. Unit 5 dBm 3 dBm At lowest power setting − 32 dBm As defined by IEEE 802.15.4, which sets a 35% maximum 15 0 − 40 Carrier frequency error Load impedance 5.5.3 Typ. 25 % + 40 ppm Ω 200 PSD mask relative 3.5MHz away − 20 dB PSD mask absolute 3.5MHz away − 30 dBm Synthesizer Table 9 lists the key parameters of the integrated synthesizer on the SN250. Table 9. Synthesizer characteristics Parameter Test Conditions Frequency range Min. Typ. 2400 Frequency resolution Max. Unit 2500 MHz 11.7 kHz Lock time From off, with correct VCO DAC setting 100 μs Relock time Channel change or RX/TX turnaround (IEEE 802.15.4 defines 192μs turnaround time) 100 μs Phase noise at 100kHz − 71 dBc/Hz Phase noise at 1MHz − 91 dBc/Hz Phase noise at 4MHz − 103 dBc/Hz Phase noise at 10MHz − 111 dBc/Hz 19/130 Functional description—system modules 6 SN250 Functional description—system modules The SN250 contains a dual-thread mode of operation—System Mode and Application Mode—to guarantee microcontroller bandwidth to the application developer and protect the developer from errant software access. During System Mode, all areas including the RF Transceiver, MAC, Packet Trace Interface, Sleep Timer, Power Management Module, Watchdog Timer, and Power on Reset Module are accessible. Since the SN250 comes with a license to ZNet, a ZigBee-compliant software stack developed by Ember Corporation, these areas are not available to the application developer in Application Mode. The following brief description of these modules provides the necessary background on the operation of the SN250. For more information, please contact your nearest STMicroelectronics sales office. 6.1 Receive (RX) path The SN250 RX path spans the analog and digital domains. The RX architecture is based on a low-IF, super-heterodyne receiver. It utilizes differential signal paths to minimize noise interference. The input RF signal is mixed down to the IF frequency of 4MHz by I and Q mixers. The output of the mixers is filtered and combined prior to being sampled by a 12Msps ADC. The RX filtering within the RX path has been designed to optimize the coexistence of the SN250 with other 2.4GHz transceivers, such as the IEEE 802.11g and Bluetooth. 6.1.1 RX baseband The SN250 RX baseband (within the digital domain) implements a coherent demodulator for optimal performance. The baseband demodulates the O-QPSK signal at the chip level and synchronizes with the IEEE 802.15.4-2003 preamble. Once a packet preamble is detected, it de-spreads the demodulated data into 4-bit symbols. These symbols are buffered and passed to the hardware-based MAC module for filtering. In addition, the RX baseband provides the calibration and control interface to the analog RX modules, including the LNA, RX Baseband Filter, and modulation modules. The ZNet software includes calibration algorithms which use this interface to reduce the effects of process and temperature variation. 6.1.2 RSSI and CCA The SN250 calculates the RSSI over an 8-symbol period as well as at the end of a received packet. It utilizes the RX gain settings and the output level of the ADC within its algorithm. The SN250 RX baseband provides support for the IEEE 802.15.4-2003 required CCA methods summarized in Table 10. Modes 1, 2, and 3 are defined by the 802.15.4-2003 standard; Mode 0 is a proprietary mode. 20/130 SN250 Functional description—system modules Table 10. CCA Mode 6.2 CCA Mode Behavior Mode Behavior 0 Clear channel reports busy medium if either carrier sense OR RSSI exceeds their thresholds. 1 Clear channel reports busy medium if RSSI exceeds its threshold. 2 Clear channel reports busy medium if carrier sense exceeds its threshold. 3 Clear channel reports busy medium if both RSSI AND carrier sense exceed their thresholds. Transmit (TX) path The SN250 transmitter utilizes both analog circuitry and digital logic to produce the O-QPSK modulated signal. The area-efficient TX architecture directly modulates the spread symbols prior to transmission. The differential signal paths increase noise immunity and provide a common interface for the external balun. 6.2.1 TX baseband The SN250 TX baseband (within the digital domain) performs the spreading of the 4-bit symbol into its IEEE 802.15.4-2003-defined 32-chip I and Q sequence. In addition, it provides the interface for software to perform the calibration of the TX module in order to reduce process, temperature, and voltage variations. 6.2.2 TX_ACTIVE signal Even though the SN250 provides an output power suitable for most ZigBee applications, some applications will require an external power amplifier (PA). Due to the timing requirements of IEEE 802.15.4-2003, the SN250 provides a signal, TX_ACTIVE, to be used for external PA power management and RF Switching logic. When in TX, the TX Baseband drives TX_ACTIVE high (as described in Table 6). When in RX, the TX_ACTIVE signal is low. If an external PA is not required, then the TX_ACTIVE signal should be connected to GND through a 100 kΩ resistor, as shown in the application circuit in Figure 16. 6.3 Integrated MAC module The SN250 integrates critical portions of the IEEE 802.15.4-2003 MAC requirements in hardware. This allows the microcontroller to provide greater bandwidth to application and network operations. In addition, the hardware acts as a first-line filter for non-intended packets. The SN250 MAC utilizes a DMA interface to RAM memory to further reduce the overall microcontroller interaction when transmitting or receiving packets. When a packet is ready for transmission, the software configures the TX MAC DMA by indicating the packet buffer RAM location. The MAC waits for the backoff period, then transitions the baseband to TX mode and performs channel assessment. When the channel is clear, the MAC reads data from the RAM buffer, calculates the CRC, and provides 4-bit symbols to the baseband. When the final byte has been read and sent to the baseband, the CRC remainder is read and transmitted. 21/130 Functional description—system modules SN250 The MAC resides in RX mode most of the time, and different format and address filters keep non-intended packets from using excessive RAM buffers, as well as preventing the CPU from being interrupted. When the reception of a packet begins, the MAC reads 4-bit symbols from the baseband and calculates the CRC. It assembles the received data for storage in a RAM buffer. A RX MAC DMA provides direct access to the RAM memory. Once the packet has been received, additional data is appended to the end of the packet in the RAM buffer space. The appended data provides statistical information on the packet for the software stack. The primary features of the MAC are: 6.4 ● CRC generation, appending, and checking ● Hardware timers and interrupts to achieve the MAC symbol timing ● Automatic preamble, and SFD pre-pended to a TX packet ● Address recognition and packet filtering on received packets ● Automatic acknowledgement transmission ● Automatic transmission of packets from memory ● Automatic transmission after backoff time if channel is clear (CCA) ● Automatic acknowledgement checking ● Time stamping of received and transmitted messages ● Attaching packet information to received packets (LQI, RSSI, gain, time stamp, and packet status) ● IEEE 802.15.4 timing and slotted/unslotted timing Packet Trace Interface (PTI) The SN250 integrates a true PHY-level PTI for effective network-level debugging. This twosignal interface monitors all the PHY TX and RX packets (in a non-intrusive manner) between the MAC and baseband modules. It is an asynchronous 500 Kbps interface and cannot be used to inject packets into the PHY/MAC interface. The two signals from the SN250 are the frame signal (PTI_EN) and the data signal (PTI_DATA). The PTI is supported by InSight Desktop. 6.5 XAP2b microprocessor The SN250 integrates the XAP2b microprocessor developed by Cambridge Consultants Ltd., making it a true system-on-a-chip solution. The XAP2b is a 16-bit Harvard architecture processor with separate program and data address spaces. The word width is 16 bits for both the program and data sides. Data-side addresses are always specified in bytes, though they can be accessed as either bytes or words, while program-side addresses are always specified and accessed as words. The data-side address bus is effectively 15 bits wide, allowing for an address space of 32KB; the program-side address bus is 16 bits wide, addressing 64k words. The standard XAP2 microprocessor and accompanying software tools have been enhanced to create the XAP2b microprocessor used in the SN250. The XAP2b adds data-side byte addressing support to the XAP2 by utilizing the 15th bit of the data-side address bus to indicate byte or word accesses. This allows for more productive usage of RAM, optimized code, and a more familiar architecture for customers when compared to the standard XAP2. 22/130 SN250 Functional description—system modules The XAP2b clock speed is 12MHz. When used with the ZNet stack, code is loaded into Flash memory over the air or by a serial link using a built-in bootloader in a reserved area of the Flash. Alternatively, code may be loaded via the SIF interface with the assistance of RAM-based utility routines also loaded via SIF. The XAP2b in the SN250 has also been enhanced to support two separate protection levels. The ZNet stack runs in System Mode, which allows full, unrestricted access to all areas of the chip, while application code runs in Application Mode. When running in Application Mode, writing to certain areas of memory and registers is restricted to prevent common software bugs from interfering with the operation of the ZNet stack. These errant writes are captured and details are reported to the developer to assist in tracking down and fixing these issues. 6.6 Embedded memory As shown in Figure 3, the program side of the address space contains mappings to both integrated Flash and RAM blocks. Figure 3. Program address space The data side of the address space contains mappings to the same Flash and RAM blocks, as well as registers and a separate Flash information area, as shown in Figure 4. 23/130 Functional description—system modules Figure 4. 6.6.1 SN250 Data address space Flash memory The SN250 integrates 128KB of Flash memory. The Flash cell has been qualified for a data retention time of >100 years at room temperature. Each Flash page size is 1024 bytes and is rated to have a guaranteed 1,000 write/erase cycles. The Flash memory has mappings to both the program and data side address spaces. On the program side, the first 112KB of the Flash memory are mapped to the corresponding first 56k word addresses to allow for code storage, as shown in Figure 3. On the program side, the Flash is always read as whole words. On the data side, the Flash memory is divided into eight 16KB sections, which can be separately mapped into a Flash window for the storage of constant data and the Simulated EEPROM. As shown in Figure 4, the Flash window corresponds to the first 16KB of the data-side address space. On the data side, the Flash may be read as bytes, but can only be written to one word at a time using utility routines in the ZNet stack and HAL. 6.6.2 Simulated EEPROM The ZNet stack reserves a section of Flash memory to provide Simulated EEPROM storage area for stack and customer tokens. Therefore, the SN250 utilizes 8KB of upper Flash storage. This section of Flash is only accessible when mapped to the Flash window in the data-side address space. Because the Flash cells are qualified for up to 1,000 write cycles, 24/130 SN250 Functional description—system modules the Simulated EEPROM implements an effective wear-leveling algorithm which effectively extends the number of write cycles for individual tokens. 6.6.3 Flash Information Area (FIA) The SN250 also includes a separate 1024-byte FIA that can be used for storage of data during manufacturing, including serial numbers and calibration values. This area is mapped to the data side of the address space, starting at address 0x5000. While this area can be read as individual bytes, it can only be written to one word at a time, and may only be erased as a whole. Programming of this special Flash page can only be enabled using the SIF interface to prevent accidental corruption or erasure. The ZNet stack reserves a small portion of this space for its own use, but the rest is available to the application. 6.6.4 RAM The SN250 integrates 5KB of SRAM. Like the Flash memory, this RAM is also mapped to both the program and data-side address spaces. On the program side, the RAM is mapped to the top 2.5k words of the program address space. The program-side mapping of the RAM is used for code when writing to or erasing the Flash memory. On the data side, the RAM is also mapped to the top of the address space, occupying the last 5KB, as shown in Figure 3 and Figure 4. Additionally, the SN250 supports a protection mechanism to prevent application code from overwriting system data stored in the RAM. To enable this, the RAM is segmented into 32byte sections, each with a configurable bit that allows or denies write access when the SN250 is running in Application Mode. Read access is always allowed to the entire RAM, and full access is always allowed when the SN250 is running in System Mode. The ZNet stack intelligently manages this protection mechanism to assist in tracking down many common application errors. 6.6.5 Registers Table 40 provides a short description of all application-accessible registers within the SN250. Complete descriptions are provided at the end of each applicable Functional Description section. The registers are mapped to the data-side address space starting at address 0x4000. These registers allow for the control and configuration of the various peripherals and modules. The registers may only be accessed as whole word quantities; attempts to access them as bytes may result in undefined behavior. There are additional registers used by the ZNet stack when the SN250 is running in System Mode, allowing for control of the MAC, baseband, and other internal modules. These system registers are protected from being modified when the SN250 is running in Application Mode. 6.7 Encryption accelerator The SN250 contains a hardware AES encryption engine that is attached to the CPU using a memory-mapped interface. NIST-based CCM, CCM*, CBC-MAC, and CTR modes are implemented in hardware. These modes are described in the IEEE 802.15.4-2003 specification, with the exception of CCM*, which is described in the ZigBee Security Services Specification 1.0. The ZNet stack implements a security API for applications that require security at the application level. 25/130 Functional description—system modules 6.8 SN250 Reset detection The SN250 contains multiple reset sources. The reset event is logged into the reset source register, which lets the CPU determine the cause of the last reset. The following reset causes are detected: 6.9 ● Power-on-Reset ● Watchdog ● PC rollover ● Software reset ● Core Power Dip Power-on-Reset (POR) Each voltage domain (1.8V Digital Core Supply VDD_CORE and Pads Supply VDD_PADS) has a power-on-reset (POR) cell. The VDD_PADS POR cell holds the always-powered high-voltage domain in reset until the following conditions have been met: ● The high-voltage Pads Supply VDD_PADS voltage rises above a threshold. ● The internal RC clock starts and generates three clock pulses. ● The 1.8V POR cell holds the main digital core in reset until the regulator output voltage rises above a threshold. Additionally, the digital domain counts 1,024 clock edges on the 24MHz crystal before releasing the reset to the main digital core. Table 11 lists the features of the SN250 POR circuitry. Table 11. POR specifications Parameter 6.10 Min. Typ. Max. Unit VDD_PADS POR release 1.0 1.2 1.4 V VDD_PADS POR assert 0.5 0.6 0.7 V 1.8V POR release 1.35 1.5 1.65 V 1.8V POR hysteresis 0.08 0.1 0.12 V Clock sources The SN250 integrates three oscillators: a high-frequency 24MHz crystal oscillator, an optional low-frequency 32.768kHz crystal oscillator, and a low-frequency internal 10kHz RC oscillator. 6.10.1 High-frequency crystal oscillator The integrated high-frequency crystal oscillator requires an external 24MHz crystal with an accuracy of ± 40ppm. Based upon the application Bill of Materials and current consumption requirements, the external crystal can cover a range of ESR requirements. For a lower ESR, the cost of the crystal increases but the overall current consumption decreases. Likewise, for 26/130 SN250 Functional description—system modules higher ESR, the cost decreases but the current consumption increases. Therefore, the designer can choose a crystal to fit the needs of the application. Table 12 lists the specifications for the high-frequency crystal. Table 12. High-frequency crystal specifications Parameter Test Conditions Min. Frequency Typ. 24 Duty cycle 40 Phase noise from 1kHz to 100kHz 6.10.2 Max. − 40 Unit MHz 60 % − 120 dBc/Hz + 40 ppm Accuracy Initial, temperature, and aging Crystal ESR Load capacitance of 10pF 100 Ω Crystal ESR Load capacitance of 18pF 60 Ω Start-up time to stable clock (max. bias) 1 ms Start-up time to stable clock (optimum bias) 2 ms 0.3 mA 0.5 mA 1 mA Current consumption Good crystal: 20Ω ESR, 10pF load Current consumption Worst-case crystals (60Ω, 18pF or 100Ω, 10pF) Current consumption At maximum bias 0.2 Low-frequency oscillator The optional low-frequency crystal source for the SN250 is a 32.768kHz crystal. Table 13 lists the requirements for the low-frequency crystal. The low-frequency crystal may be used for applications that require greater accuracy than can be provided by the internal RC oscillator. The crystal oscillator has been designed to accept any standard watch crystal with an ESR of 100 kΩ. Table 13. Low-Frequency Crystal Specifications Parameter Test Conditions Min. Frequency Accuracy Load capacitance (double this each side to ground) Typ. Max. 32.768 Initial, temperature, and aging − 100 Unit kHz + 100 12.5 ppm pF Crystal ESR 100 kΩ Start-up time 1 S 0.5 μA Current consumption 27/130 Functional description—system modules 6.10.3 SN250 Internal RC oscillator The SN250 has a low-power, low-frequency RC oscillator that runs all the time. Its nominal frequency is 10kHz. The RC oscillator has a coarse analog trim control, which is first adjusted to get the frequency as close to 10kHz as possible. This raw clock is used by the chip management block. It is also divided down to 1kHz using a variable divider to allow software to accurately calibrate it. This calibrated clock is available to the sleep timer. Timekeeping accuracy depends on temperature fluctuations the chip is exposed to, power supply impedance, and the calibration interval, but in general it will be better than 150ppm (including crystal error of 40ppm). Table 14 lists the specifications of the RC oscillator. Table 14. RC Oscillator Specifications Parameter Min. Typ. Max. Unit Frequency 10 kHz Analog trim steps 1 kHz Frequency variation with supply 6.11 Test Conditions For a voltage drop from 3.6V to 3.1V or 2.6V to 2.1V 0.5 % Random number generator The SN250 allows for the generation of random numbers by exposing a randomly generated bit from the RX ADC. Analog noise current is passed through the RX path, sampled by the receive ADC, and stored in a register. The value contained in this register could be used to seed a software-generated random number. The ZNet stack utilizes these random numbers to seed the Random MAC Backoff and Encryption Key Generators. 6.12 Watchdog timer The SN250 contains a watchdog timer clocked from the internal oscillator. The watchdog is disabled by default, but can be enabled or disabled by software. If the timer reaches its time-out value of approximately 2 seconds, it will generate a reset signal to the chip. When software is running properly, the application can periodically restart this timer to prevent the reset signal from being generated. The watchdog will generate a low watermark interrupt in advance of actually resetting the chip. This low watermark interrupt occurs approximately 1.75 seconds after the timer has been restarted. This interrupt can be used to assist during application debug. 28/130 SN250 6.13 Functional description—system modules Sleep timer The 16-bit sleep timer is contained in the always-powered digital block. It has the following features: ● Two output compare registers, with interrupts ● Only Compare A Interrupt generates Wake signal ● Further clock divider of 2N, for N = 0 to 10 The clock source for the sleep timer can be either the 32.768 kHz clock or the calibrated 1kHz clock (see Table 15). After choosing the clock source, the frequency is slowed down with a 2N prescaler to generate the final timer clock (see Table 16). Legal values for N are 0 to 10. The slowest rate the sleep timer counter wraps is 216 ∗ 210 / 1kHz ≈ 67109 sec. ≈ about 1118.48 min. ≈ 18.6 hrs. Table 15. Sleep timer clock source selection CLK_SEL Clock Source 0 Calibrated 1kHz clock 1 32.768kHz clock Table 16. Sleep timer clock source prescaling CLK_DIV[3:0] Clock Source Prescale Factor N = 0..10 2N N = 11..15 210 The ZNet software allows the application to define the clock source and prescaler value. Therefore, a programmable sleep/wake duty cycle can be configured according to the application requirements. 6.14 Power management The SN250 supports three different power modes: processor ACTIVE, processor IDLE, and DEEP SLEEP. The IDLE power mode stops code execution of the XAP2b until any interrupt occurs or an external SIF wakeup command is seen. All peripherals of the SN250 including the radio continue to operate normally. The DEEP SLEEP power mode powers off most of the SN250 but leaves the critical chip functions, such as the GPIO pads and RAM powered by the High Voltage Supply (VDD_PADS). The SN250 can be woken by configuring the sleep timer to generate an interrupt after a period of time, using an external interrupt, or with the SIF interface. Activity on a serial interface may also be configured to wake the SN250, though actual reception of data is not re-enabled until the SN250 has finished waking up. Depending on the speed of the serial data, it is possible to finish waking up in the middle of a byte. Care must be taken to reset the serial interface between bytes and discard any garbage data before the rest. Another condition for wakeup is general activity on GPIO pins. The GPIO activity monitoring is described in Section 7.1. When in DEEP SLEEP, the internal regulator is disabled and VREG_OUT is turned off. All GPIO output signals are maintained in a frozen state. Additionally, the state of all registers in 29/130 Functional description—system modules SN250 the powered-down low-voltage domain of the SN250 is lost. Register settings for application peripherals should be preserved by the application as desired. The operation of DEEP SLEEP is controlled by ZNet APIs which automatically preserve the state of necessary system peripherals. The internal XAP2b CPU registers are automatically saved and restored to RAM by hardware when entering and leaving the DEEP SLEEP mode, allowing code execution to continue from where it left off. The event that caused the wakeup and any additional events that occurred while waking up are reported to the application via the ZNet APIs. Upon waking from DEEP SLEEP, the internal regulator is re-enabled. 30/130 SN250 7 Functional description—application modules Functional description—application modules In Application Mode, access to privileged areas are blocked while access to applicationspecific modules such as GPIO, Serial Controllers (SC1 and SC2), General Purpose Timers, ADC, and Event Manager are enabled. 7.1 GPIO The SN250 has 17 multi-purpose GPIO pins that can be configured in a variety of ways. All pins have the following programmable features: ● Selectable as input, output, or bi-directional. ● Output can be totem pole, used as open drain or open source output for wired-OR applications. ● Can have internal pull-up or pull-down. The information flow between the GPIO pin and its source are controlled by separate GPIO Data registers. The GPIO_INH and GPIO_INL registers report the input level of the GPIO pins. The GPIO_DIRH and GPIO_DIRL registers enable the output signals for the GPIO Pins. The GPIO_PUH and GPIO_PUL registers enable pull-up resistors while GPIO_PDH and GPIO_PDL registers enable pull-down resistors on the GPIO Pins. The GPIO_OUTH and GPIO_OUTL control the output level. Instead of changing the entire contents to the OUT/DIR registers with one write access, a limited change can be applied. Writing to the GPIO_SETH/L or GPIO_DIRSETH/L register changes individual register bits from 0 to 1, while data bits that are already 1 are maintained. Writing to the GPIO_CLRH/L or GPIO_DIRCLRH/L register changes individual register bits from 1 to 0, while data bits that are already 0 are maintained. Note that the value read from GPIO_OUTH/L, GPIO_SETH/L, and GPIO_CLRH/L registers may not reflect the current pin state. To observe the pin state, the GPIO_INH/L registers should be read. All registers controlling the GPIO pin definitions are unaffected by power cycling the main core voltage (VDD_CORE). 31/130 Functional description—application modules Figure 5. SN250 GPIO control logic VDD_PADS GPIO_PUH/L GPIO_DIRSETH/L GPIO_DIRH/L GPIO_DIRCLRH/L GPIO_SETH/L GPIO_OUTH/L GPIO_CLRH/L Alternate GPIO functions Note (1) Note (2) GPIO_CFG GPIO[16:0] GPIO_PDH/L GPIO_INH/L Note (1) : Pull-up resistor is always disabled for Alternate GPIO functions ADC 0, ADC1, ADC2, ADC3, VREF_OUT, PTI_EN and PTI_DATA. Note (2) : Pull-down resistor is always disabled for Alternate GPIO functions VREF_OUT, PTI_EN and PTI_DATA. The GPIO_DBG register must always remain set to zero. The GPIO_CFG register controls the GPIO signal routing for alternate GPIO functions as listed in Table 17. Refer to Table 1 for individual pin alternate functions. Table 18 defines the alternate functions routed to the GPIO. To allow more flexibility, the timer signals can come from alternative sources (e.g., TIM1IA.1, TIM1IA.2, TIM1IA.3), depending on what serial controller functions are used. The Always Connected input functions labelled IRQA, IRQB, IRQC and IRQD refer to the external interrupts. GPIO8, GPIO14, GPIO15, and GPIO16 are the only pins designed to operate as external interrupts (IRQs). These pins offer individual filtering options, triggering options, and interrupt configurations. The minimum width needed to latch an unfiltered external interrupt in both level and edge triggered mode is 80ns. With the filter engaged via the GPIO_INTFIlT bit, the minimum width needed in 450ns. Other alternate functions such as timer input captures are capable of generating an interrupt based on external signals, but these other alternate functions do not contain the flexibility offered on the four external interrupts (IRQs). When the core is powered down, peripherals stop driving correct output signals. To maintain correct output signals, the system software will ensure that the GPIO output signals are frozen before going into deep sleep. Monitoring circuitry is in place to detect when the logic state of GPIO input pins change. The lower 16 GPIO pins that should be monitored can be chosen by software with the GPIO_WAKEL register. The resulting event can be used for waking up from deep sleep as described in Section 6.14. 32/130 SN250 Table 17. Functional description—application modules GPIO pin configurations GPIO_CFG[15:0] Mode 0010 0000 0000 0000 DEFAULT ---1 ---- ---- ---- Enable PTI_EN + PTI_DATA ---0 ---1 ---- ---- Enable analog input ADC0 ---0 ---0 ---- ---- EnableGPIO4 ---0 --1- ---- ---- Enable analog input ADC1 ---0 --0- ---- ---- Enable GPIO5 Enable GPIO6 Enable GPIO7 Enable GPIO8 ---- -1-- ---- ---- Enable analog input ADC2 ---- -0-- ---- -----1- ---- ---- ---- Enable REG_EN --0- 1--- ---- ---- Enable analog input ADC3 --0- 0--- ---- ----1-- ---- ---- ---- Enable VREF_OUT -0-- ---- ---- ------- ---- 0000 ---- Enable ---- ---- 0001 ---- Enable SC1-2 + CAP2-0 + CAP1-0 mode+ GPIO[12,11,10,9,3,2,1,0] + SC2-2 + CAP2-0 + CAP1-0 mode+GPIO[12,11, 3, 0] ---- ---- 0010 ---- Enable SC1-4A + SC2-4S + CAP2-2 + CAP1-2h mode ---- ---- 0011 ---- Enable SC1-3M + SC2-3M + CAP2-2 + CAP1-2 mode+GPIO[12, ---- ---- 0100 ---- Enable mode+GPIO[12,11,10,9,3, ---- ---- 0101 ---- Enable SC1-2 SC2-2 + CAP2-0 + CAP1-0 3 + SC2-4S + CAP2-0 + CAP1-2h mode+GPIO[12,11 ] 0] ] ---- ---- 0110 ---- Enable SC1-4A + SC2-3M + CAP2-2 + CAP1-2 mode+GPIO[ 3 ---- ---- 0111 ---- Enable SC1-3M mode+GPIO[12 3,2,1,0] ---- ---- 1000 ---- Enable ---- ---- 1001 ---- Enable SC1-2 + CAP2-1 + CAP1-0 SC2-4S + CAP2-0 + CAP1-1h mode+GPIO[12,11,10,9 + SC2-3M + CAP2-0 + CAP1-2 ---- ---- 1010 ---- Enable SC1-4A ---- ---- 1011 ---- Enable SC1-3M + SC2-2 ---- ---- 1100 ---- Enable ] ] mode+GPIO[12,11, 3 + CAP2-1 + CAP1-0 mode+GPIO[ 3,2,1,0] + CAP2-2 + CAP1-0 mode+GPIO[12 3, SC2-3M + CAP2-0 + CAP1-1 mode+GPIO[12,11,10,9,3 ] 0] ] ---- ---- 1101 ---- Enable SC1-2 + CAP2-0 + CAP1-0 mode+GPIO[12,11, 3,2,1,0] ---- ---- 1110 ---- Enable SC1-4A + SC2-2 + CAP2-2 + CAP1-0 mode+GPIO[ 3, ---- ---- 1111 ---- Enable SC1-3M + SC2-4S + CAP2-2 + CAP1-2h mode+GPIO[12 0] ] ---- ---- ---- ---1 Enable TMR2OA ---- ---- ---- ---0 Enable GPIO13 ---- ---- ---- --1- Enable TMR2OB ---- ---- ---- --0- Enable GPIO14 ---- ---- ---- -1-- Enable TMR1OA ---- ---- ---- -0-- Enable GPIO15 ---- ---- ---- 1--- Enable TMR1OB ---- ---- ---- 0--- EnableGPIO16 33/130 Functional description—application modules Table 18. SN250 GPIO pin functions Always GPIO Connected Pin Input Functions Timer Functions Serial Digital Functions 0 IO TMR1IA.1 (when CAP1-0 mode) MOSI Standard 1 IO TMR2IA.2 (when CAP2-1 mode) MISO / SDA Standard 2 IO TMR2IB.2 (when CAP2-1 mode) MSCLK / SCL Standard 3 IO TMR1IB.1 (when CAP1-0 mode) nSSEL (input) Standard 4 IO PTI_EN ADC0 input Standard 5 IO PTI_DATA ADC1 input Standard 6 IO ADC2 input Standard 7 IO ADC3 input Standard 8 IO / IRQA TMR1CLK, TMR2ENMSK VREF_OUT Standard 9 IO TMR1IA.2 TXD / MO / MSDA (when CAP1-1 or CAP1-1h mode) Standard 10 IO TMR1IB.2 (when CAP1-1 mode) RXD / MI / MSCL Standard 11 IO TMR2IA.1 (when CAP2-0 mode) nCTS / MCLK Standard 12 IO TMR2IB.1 (when CAP2-0 mode) nRTS Standard 13 IO TMR2OA TMR1IA.3 (when CAP1-2h or CAP1-2 mode) High 14 IO / IRQB TMR2OB TMR1IB.3 (when CAP1-2 mode) High 15 IO / IRQC TMR1OA TMR2IA.3 (when CAP2-2 mode) High 16 IO / IRQD TMR1OB TMR2IB.3 (when CAP2-2 mode) High 34/130 TMR2CLK, TMR1ENMSK REG_EN (open collector enable for external regulator) Analog Function Output Current Drive SN250 7.1.1 Functional description—application modules Registers GPIO_CFG [0x4712] 15 0-R 14 0-RW 13 1-RW 12 0-RW 0 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 GPIO_CFG GPIO_CFG 0-RW 7 GPIO_CFG 0-RW 6 [14:0] 0-RW 5 0-RW 4 0-RW 3 GPIO configuration modes. Refer to Table 1 and Table 17 for the mode settings. GPIO_INH [0x4700] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_INH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 11 0-R 10 0-R 9 0-R 8 0-R 0-R 3 0-R 2 0-R 1 0-R 0 GPIO_INH [0] Read the input level of GPIO[16] pin. GPIO_INL [0x4702] 15 0-R 14 0-R 13 0-R 12 0-R GPIO_INL GPIO_INL 0-R 7 GPIO_INL 0-R 6 [15:0] 0-R 5 0-R 4 Read the input level of GPIO[15:0] pins. 35/130 Functional description—application modules SN250 GPIO_OUTH [0x4704] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_OUTH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 GPIO_OUTH [0] Write the output level of GPIO[16] pin. The value read may not match the actual value on the pin. GPIO_OUTL [0x4706] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 GPIO_OUTL GPIO_OUTL 0-RW 7 GPIO_OUTL 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 Write the output level of GPIO[15:0] pins. The value read may not match the actual value on the pin. GPIO_SETH [0x4708] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_SETH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-W 0 GPIO_SETH [0] 36/130 Set the output level of GPIO[16] pin. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_OUTH to become 1. SN250 Functional description—application modules GPIO_SETL [0x470A] 15 0-W 14 0-W 13 0-W 12 0-W 11 0-W 10 0-W 9 0-W 8 0-W 0-W 2 0-W 1 0-W 0 GPIO_SETL GPIO_SETL 0-W 7 GPIO_SETL 0-W 6 [15:0] 0-W 5 0-W 4 0-W 3 Set the output level of GPIO[15:0] pins. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_OUTL to become 1. GPIO_CLRH [0x470C] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_CLRH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-W 0 GPIO_CLRH [0] Clear the output level of GPIO[16] pin. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_OUTH to become 0. GPIO_CLRL [0x470E] 15 0-W 14 0-W 13 0-W 12 0-W 11 0-W 10 0-W 9 0-W 8 0-W 0-W 2 0-W 1 0-W 0 GPIO_CLRL GPIO_CLRL 0-W 7 GPIO_CLRL 0-W 6 [15:0] 0-W 5 0-W 4 0-W 3 Clear the output level of GPIO[15:0] pins. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_OUTL to become 0. 37/130 Functional description—application modules SN250 GPIO_DIRH [0x4714] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_DIRH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 GPIO_DIRH [0] Enable the output of GPIO[16] pin. GPIO_DIRL [0x4716] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 GPIO_DIRL GPIO_DIRL 0-RW 7 GPIO_DIRL 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 Enable the output of GPIO[15:0] pins. GPIO_DIRSETH [0x4718] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_ DIRSETH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-W 0 GPIO_DIRSETH 38/130 [0] Set the output enable of GPIO[16] pin. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_DIRH to become 1. SN250 Functional description—application modules GPIO_DIRSETL [0x471A] 15 0-W 14 0-W 13 0-W 12 0-W 11 0-W 10 0-W 9 0-W 8 0-W 0-W 2 0-W 1 0-W 0 GPIO_DIRSETL GPIO_DIRSETL 0-W 7 GPIO_DIRSETL 0-W 6 [15:0] 0-W 5 0-W 4 0-W 3 Set the output enable of GPIO[15:0] pins. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_DIRL to become 1. GPIO_DIRCLRH [0x471C] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_ DIRCLRH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-W 0 GPIO_DIRCLRH [0] Clear the output enable of GPIO[16] pin. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_DIRH to become 0. GPIO_DIRCLRL [0x471E] 15 0-W 14 0-W 13 0-W 12 0-W 11 0-W 10 0-W 9 0-W 8 0-W 0-W 2 0-W 1 0-W 0 GPIO_DIRCLRL GPIO_DIRCLRL 0-W 7 GPIO_DIRCLRL 0-W 6 [15:0] 0-W 5 0-W 4 0-W 3 Clear the output enable of GPIO[15:0] pins. Only writing ones into this register will have an effect. Any bit that has one written to it will cause the corresponding bit in GPIO_DIRL to become 0. 39/130 Functional description—application modules SN250 GPIO_PDH [0x4720] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_PDH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 GPIO_PDH [0] Set this bit to enable pull-down resistors on GPIO[16] pin. GPIO_PDL [0x4722] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 GPIO_PDL GPIO_PDL 0-RW 7 GPIO_PDL 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 Set this bit to enable pull-down resistors on GPIO[15:0] pins. GPIO_PUH [0x4724] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 GPIO_PUH 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 GPIO_PUH [0] 40/130 Set this bit to enable pull-up resistors on GPIO[16] pin. SN250 Functional description—application modules GPIO_PUL [0x4726] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 GPIO_PUL GPIO_PUL 0-RW 7 0-RW 6 GPIO_PUL [15:0] 0-RW 5 0-RW 4 0-RW 3 Set this bit to enable pull-up resistors on GPIO[15:0] pins. GPIO_WAKEL [0x4728] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW GPIO_WAKEL GPIO_WAKEL 0-RW 7 0-RW 6 GPIO_WAKEL [15:0] 0-RW 5 0-RW 4 0-RW 3 Setting bits will enable GPIO wakeup monitoring for changing states on GPIO[15:0] pins. GPIO_INTCFGA [0x4630] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 GPIO_ INTFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 GPIO_INTMOD 0-RW 7 0-RW 6 0-RW 5 GPIO_INTFILT [8] Set this bit to enable GPIO IRQA filter. GPIO_INTMOD [7:5] GPIO IRQA input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges; 4 = active high triggered; 5 = active low trigger; 6,7 = reserved. 41/130 Functional description—application modules SN250 GPIO_INTCFGB [0x4632] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 GPIO_INTFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 GPIO_INTMOD 0-RW 7 0-RW 6 0-RW 5 GPIO_INTFILT [8] Set this bit to enable GPIO IRQB filter GPIO_INTMOD [7:5] GPIO IRQB input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges; 4 = active high triggered; 5 = active low trigger; 6,7 = reserved. GPIO_INTCFGC [0x4634] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 GPIO_INTFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 GPIO_INTMOD 0-RW 7 0-RW 6 0-RW 5 GPIO_INTFILT [8] Set this bit to enable GPIO IRQC filter. GPIO_INTMOD [7:5] GPIO IRQC input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges; 4 = active high triggered; 5 = active low trigger; 6,7 = reserved. GPIO_INTCFGD [0x4636] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 GPIO_INTFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 GPIO_INTMOD 0-RW 7 0-RW 6 0-RW 5 GPIO_INTFILT [8] Set this bit to enable GPIO IRQD filter. GPIO_INTMOD [7:5] GPIO IRQD input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges; 4 = active high triggered; 5 = active low trigger; 6,7 = reserved. 42/130 SN250 Functional description—application modules INT_GPIOCFG [0x4628] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 INT_GPIOD INT_GPIOC INT_GPIOB INT_GPIOA 0-R 7 0-R 6 0-R 5 0-R 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_GPIOD [3] GPIO IRQD interrupt enable. INT_GPIOC [2] GPIO IRQC interrupt enable. INT_GPIOB [1] GPIO IRQB interrupt enable. INT_GPIOA [0] GPIO IRQA interrupt enable. INT_GPIOFLAG [0x4610] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 INT_GPIOD INT_GPIOC INT_GPIOB INT_GPIOA 0-R 7 0-R 6 0-R 5 0-R 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_GPIOD [3] GPIO IRQD interrupt pending. INT_GPIOC [2] GPIO IRQC interrupt pending. INT_GPIOB [1] GPIO IRQB interrupt pending. INT_GPIOA [0] GPIO IRQA interrupt pending. GPIO_DBG [0x4710] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 GPIO_DBG [1:0] GPIO_DBG 0-RW 1 0-RW 0 This register must remain zero. 43/130 Functional description—application modules 7.2 SN250 Serial controller SC1 The SN250 SC1 module provides asynchronous (UART) or synchronous (SPI or I2C) serial communications. Figure 6 is a block diagram of the SC1 module. Figure 6. SC1 block diagram The full-duplex interface of the SC1 module can be configured into one of these three communication modes, but it cannot run them simultaneously. To reduce the interrupt service requirements of the CPU, the SC1 module contains buffered data management schemes for the three modes. A dedicated, buffered DMA controller is available to the SPI and UART controllers while a FIFO is available to all three modes. In addition, a SC1 data register allows the software application direct access to the SC1 data within all three modes. Finally, the SC1 routes the interface signals to GPIO pins. These are shared with other functions and are controlled by the GPIO_CFG register. For selecting alternate pin functions, please refer to Table 17 and Table 18. 44/130 SN250 7.2.1 Functional description—application modules UART mode The SC1 UART controller is enabled with SC1_MODE set to 1. The UART mode contains the following features: ● Baud rate (300 bps up to 921 Kbps) ● Data bits (7 or 8) ● Parity bits (none, odd, or even) ● Stop bits (1 or 2) The following signals can be made available on GPIO pins: ● TXD ● RXD ● nRTS (optional) ● nCTS (optional) The SC1 UART module obtains its reference baud-rate clock from a programmable baud generator. Baud rates are set by a clock division ratio from the 24MHz clock: rate = 24MHz / ( 2 ∗ ( N + (0.5 ∗ F) ) ) The integer portion, N, is written to the SC1_UARTPER register and the fractional remainder, F, to the SC1_UARTFRAC register. Table 19 lists the supported baud rates with associated baud rate error. The minimum allowable setting for SC1_UARTPER is 8. Table 19. UART baud rates Baud Rate (bps) SC1_UARTPER SC1_UARTFRAC Baud Rate Error (%) 300 40000 0 0 4800 2500 0 0 9600 1250 0 0 19200 625 0 0 38400 312 1 0 57600 208 1 − 0.08 115200 104 0 0.16 460800 26 0 0.16 921600 13 0 0.16 The UART module supports various frame formats depending upon the number of data bits (SC1_UART8BIT), the number of stop bits (SC1_UART2STP), and the parity (SC1_UARTPAR plus SC1_UARTODD). The register bits SC1_UART8BIT, SC1_UART2STP, SC1_UARTPAR, and SC1_UARTODD are defined within the SC1_UARTCFG register. In addition, the UART module supports flow control by setting SC1_UARTFLOW, SC1_UARTAUTO, and SC1_UARTRTS in the SC1_UARTCFG register (see Table 20). 45/130 Functional description—application modules Table 20. SN250 Configuration table for the UART module SC1_UARTCFG SC1_MODE SC1_UARTFLOW SC1_UARTAUTO SC1_UARTRTS GPIO_CFG[7:4] GPIO-Pin Function 1 0 - - SC1-2 mode TXD/RXD output/input 1 1 - - SC1-2 mode Illegal SC1-4A mode TXD/RXD/CTS output/input/input RTS output = ON/OFF 1 1 0 0/1 1 1 1 - SC1-4A mode TXD/RXD/CTS output/input/input RTS output = ON if 2 or more bytes will fit in receive buffer 1 0 1 - SC1-4A mode Reserved 1 0 0 - SC1-4A mode Illegal 1 - - - SC1-3M mode Illegal Characters transmitted and received are passed through transmit and receive FIFOs. The transmit and receive FIFOs are 4 bytes deep. The FIFOs are accessed under software control by accessing the SC1_DATA data register or under hardware control by the SC1 DMA. When a transmit character is written to the (empty) transmit FIFO, the register bit SC1_UARTTXIDLE in the SC1_UARTSTAT register clears to indicate that not all characters are transmitted yet. Further transmit characters can be written to the transmit FIFO until it is full, which causes the register bit SC1_UARTTXFREE in the SC1_UARTSTAT register to clear. After shifting one transmit character to the TXD pin, space for one transmit character becomes available in the transmit FIFO. This causes the register bit SC1_UARTTXFREE in the SC1_UARTSTAT register to get set. After all characters are shifted out, the transmit FIFO empties, which causes the register bit SC1_UARTTXIDLE in the SC1_UARTSTAT register to get set. A received character is stored with its parity and frame error status in the receive FIFO. The register bit SC1_UARTRXVAL in the SC1_UARTSTAT register is set to indicate that not all received characters are read out from the receive FIFO. The error status of a received byte is available with the register bits SC1_UARTPARERR and SC1_UARTFRMERR in the SC1_UARTSTAT register. When the DMA controller is transferring the data from the receive FIFO to a memory buffer, it checks the stored parity and frame error status flags. When an error is flagged, the SC1_RXERRA/B register is updated, marking the offset to the first received character with parity or frame error. When the 4-character receive FIFO contains 3 characters, flow control needs to be used to avoid an overflow event. One method is to use software handshaking by transmitting reserved XON/XOFF characters which are interpreted by the transmitting terminal to pause further transmissions (to the receive FIFO). Another method is to use hardware handshaking using XOFF assertion through the RTS signal. 46/130 SN250 Functional description—application modules There are two schemes available to assert the RTS signal. The first scheme is to initiate RTS assertion with software by setting the register bit SC1_UARTRTS in the SC1_UARTCFG register. The second scheme is to assert RTS automatically depending on the fill state of the receive FIFO. This is enabled with the register bit SC1_UARTAUTO in the SC1_UARTCFG register. The UART also contains overrun protection for both the FIFO and DMA options. If the transmitting terminal continues to transmit characters to the receive FIFO, only 4 characters are stored in the FIFO. Additional characters are dropped, and the register bit SC1_UARTRXOVF in the SC1_UARTSTAT register is set. Should this receive overrun occur during DMA operation, the SC1_RXERRA/B registers mark the error-offset. The RX FIFO hardware generates the INT_SCRXOVF interrupt, but the DMA register will not indicate the error condition until the RX FIFO is drained. Once the DMA marks a RX error, there are two conditions that will clear the error indication: setting the appropriate SC_TX/RXDMARST bit in the SC1_DMACTRL register, or loading the appropriate DMA buffer after it has unloaded. Interrupts are generated on the following events: ● Transmit FIFO empty and last character shifted out (0 to 1 transition of SC1_UARTTXIDLE) ● Transmit FIFO changed from full to not full (0 to 1 transition of SC1_UARTTXFREE) ● Receive FIFO changed from empty to not empty (0 to 1 transition of SC1_UARTRXVAL) ● Transmit DMA buffer A/B complete (1 to 0 transition of SC_TXACTA/B) ● Receive DMA buffer A/B complete (1 to 0 transition of SC_RXACTA/B) ● Character received with Parity error ● Character received with Frame error ● Received and lost character while receive FIFO was full (Receive overrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC1CFG and INT_CFG registers must be enabled. 7.2.2 SPI master mode The SPI mode of the SC1 is master mode only. It has a fixed word length of 8 bits. The SC1 SPI controller is enabled with SC1_MODE set to 2 and register bit SC_SPIMST set in the SC1_SPICFG register. The SPI mode has the following features: ● Full duplex operation ● Programmable clock frequency (12MHz max.) ● Programmable clock polarity and clock phase ● Selectable data shift direction (either LSB or MSB first) The following signals can be made available on the GPIO pins: ● MO (master out) ● MI (master in) ● MCLK (serial clock) The SC1 SPI module obtains its reference clock from a programmable clock generator. Clock rates are set by a clock division ratio from the 24MHz clock: rate = 24MHz / ( 2 ∗ (LIN + 1) ∗ 2EXP ) 47/130 Functional description—application modules SN250 EXP is written to the SC1_RATEEXP register and LIN to the SC1_RATELIN register. Since the range for both values is 0 to 15, the fastest data rate is 12Mbps and the slowest rate is 22.9bps. The SC1 SPI master supports various frame formats depending upon the clock polarity (SC_SPIPOL), clock phase (SC_SPIPHA), and direction of data (SC_SPIORD) (see Table 21). The register bits SC_SPIPOL, SC_SPIPHA, and SC_SPIORD are defined within the SC1_SPICFG register. Switching the SPI configuration from SC_SPIPOL=1 to SC_SPIPOL=0 without subsequently setting SC1_MODE=0 and reinitializing the SPI will cause an extra byte (0xFE) to be transmitted immediately before the first intended byte. Table 21. SC1 SPI master frame format SC1_MODE SC_SPIMST SC_SPIORD SC_SPIPHA SC_SPIPOL SC1_SPICFG GPIO_CFG[7:4] Note: 2 1 0 0 0 SC1-3M mode 2 1 0 0 1 SC1-3M mode 2 1 0 1 0 SC1-3M mode 2 1 0 1 1 SC1-3M mode 2 1 1 - - SC1-3M Same as above except LSB first instead of MSB first mode 2 1 - - - SC1-2 mode 2 1 - - - SC1-4A Illegal mode Frame Format Illegal Serialized SC1 SPI transmit data is driven to the output pin MO. SC1 SPI master data is received from the input pin MI. To generate slave select signals to SPI slave devices, other GPIO pins have to be used and their assertion must be controlled by software. Characters transmitted and received are passed through transmit and receive FIFOs. The transmit and receive FIFOs are 4 bytes deep. These FIFOs are accessed under software control by accessing the SC1_DATA data register or under hardware control using a DMA controller. 48/130 SN250 Functional description—application modules When a transmit character is written to the (empty) transmit FIFO, the register bit SC_SPITXIDLE in the SC1_SPISTAT register clears and indicates that not all characters are transmitted yet. Further transmit characters can be written to the transmit FIFO until it is full, which causes the register bit SC_SPITXFREE in the SC1_SPISTAT register to clear. After shifting one transmit character to the MO pin, space for one transmit character becomes available in the transmit FIFO. This causes the register bit SC_SPITXFREE in the SC1_SPISTAT register to get set. After all characters are shifted out, the transmit FIFO empties, which causes the register bit SC_SPITXIDLE in the SC1_SPISTAT register to get set also. Any character received is stored in the (empty) receive FIFO. The register bit SC_SPIRXVAL in the SC1_SPISTAT register is set to indicate that not all received characters are read out from receive FIFO. If software or DMA is not reading from the receive FIFO, the receive FIFO will store up to 4 characters. Any further reception is dropped and the register bit SC_SPIRXOVF in the SC1_SPISTAT register is set. The RX FIFO hardware generates the INT_SCRXOVF interrupt, but the DMA register will not indicate the error condition until the RX FIFO is drained. Once the DMA marks a RX error, there are two conditions that will clear the error indication: setting the appropriate SC_TX/RXDMARST bit in the SC1_DMACTRL register, or loading the appropriate DMA buffer after it has unloaded. Receiving a character always requires transmitting a character. In a case when a long stream of receive characters is expected, a long sequence of (dummy) transmit characters must be generated. To avoid software or transmit DMA initiating these transfers (and consuming unnecessary bandwidth), the SPI serializer can be instructed to retransmit the last transmitted character, or to transmit a busy token (0xFF), which is determined by the register bit SC_SPIRPT in the SC1_SPICFG register. This functionality can only be enabled (or disabled) when the transmit FIFO is empty and the transmit serializer is idle, as indicated by a cleared SC_SPITXIDLE register bit in the SC1_SPISTAT register. Every time an automatic character transmission is started, a transmit underrun is detected (as there is no data in transmit FIFO), and the register bit INT_SCTXUND in the INT_SC1FLAG register is set. Note that after disabling the automatic character transmission, the reception of new characters stops and the receive FIFO holds characters just received. Note: The event Receive DMA complete does not automatically mean receive FIFO empty. Interrupts are generated on the following events: ● Transmit FIFO empty and last character shifted out (0 to 1 transition of SC_SPITXIDLE) ● Transmit FIFO changed from full to not full (0 to 1 transition of SC_SPITXFREE) ● Receive FIFO changed from empty to not empty (0 to 1 transition of SC_SPIRXVAL) ● Transmit DMA buffer A/B complete (1 to 0 transition of SC_TXACTA/B) ● Receive DMA buffer A/B complete (1 to 0 transition of SC_RXACTA/B) ● Received and lost character while receive FIFO was full (Receive overrun error) ● Transmitted character while transmit FIFO was empty (Transmit underrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC1CFG and INT_CFG registers must be enabled. 49/130 Functional description—application modules 7.2.3 SN250 I2C master mode The SC1 I2C controller is only available in master mode. The SC1 I2C controller is enabled with SC1_MODE set to 3. The I2C Master controller supports Standard (100 Kbps) and Fast (400 Kbps) I2C modes. Address arbitration is not implemented, so multiple master applications are not supported. The I2C signals are pure open-collector signals, and external pull-up resistors are required. The SC1 I2C mode has the following features: ● Programmable clock frequency (400kHz max.) ● Supports both 7-bit and 10-bit addressing The following signals can be made available on the GPIO pins: ● MSDA (serial data) ● MSCL (serial clock) The I2C Master controller obtains its reference clock from a programmable clock generator. Clock rates are set by a clock division ratio from the 24MHz clock: 24MHz Nominal Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 EXP is written to the SC1_RATEEXP register and LIN to the SC1_RATELIN register. Table 22 shows the rate settings for Standard I2C (100 Kbps) and Fast I2C (400 Kbps) operation. Table 22. I2C nominal rate programming Nominal Rate SC1_RATELIN SC1_RATEEXP 100 Kbps 14 3 375 Kbps 15 1 400 Kbps 14 1 Note that at 400 Kbps, the I2C specification requires the minimum low period of SCL to be 1.3µs. To be strictly I2C compliant, the rate needs to be lowered to 375 Kbps. The I2C Master controller supports generation of various frame segments controlled with the register bits SC_I2CSTART, SC_I2CSTOP, SC_I2CSEND, and SC_I2CRECV in the SC1_I2CCTRL1 registers. Table 23 summarizes these frames. 50/130 SN250 Functional description—application modules SC1 I2C master frame segments Table 23. SC1_MODE SC_I2CSTART SC_I2CSEND SC_I2CRECV SC_I2CSTOP GPIO_CFG[7:4] SC1_I2CCTRL1 3 1 0 0 0 SC1-2 mode 3 0 1 0 0 SC1-2 mode 3 0 0 1 0 SC1-2 mode 3 0 0 0 1 SC1-2 mode 3 0 0 0 0 SC1-2 mode No pending frame segment 3 1 1 1 1 - 1 1 - 1 1 SC1-2 mode Illegal Frame Segments 51/130 Functional description—application modules SN250 SC1 I2C master frame segments (continued) Table 23. SC1_MODE SC_I2CSTART SC_I2CSEND SC_I2CRECV SC_I2CSTOP GPIO_CFG[7:4] SC1_I2CCTRL1 3 - - - - SC1-4M Illegal mode 3 - - - - SC1-4A Illegal mode Frame Segments Full I2C frames have to be constructed under software control by generating individual I2C segments. All necessary segment transitions are shown in Figure 7. ACK or NACK generation of an I2C receive frame segment is determined with the register bit SC_I2CACK in the SC1_I2CCTRL2 register. Figure 7. I2C segment transitions Generation of a 7-bit address is accomplished with one transmit segment. The upper 7 bits of the transmitted character contain the 7-bit address. The remaining lower bit contains the command type (“read” or “write”). Generation of a 10-bit address is accomplished with two transmit segments. The upper 5 bits of the first transmit character must be set to 0x1E. The next 2 bits are for the 2 most significant bits of the 10-bit address. The remaining lower bit contains the command type 52/130 SN250 Functional description—application modules (“read” or “write”). The second transmit segment is for the remaining 8 bits of the 10-bit address. Characters received and transmitted are passed through receive and transmit FIFOs. The SC1 I2C master transmit and receive FIFOs are 1-byte deep. These FIFOs are accessed under software control. (Re)start and stop segments are initiated by setting the register bits SC_I2CSTART or SC_I2CSTOP in the SC1_I2CCTRL1 register followed by waiting until they have cleared. Alternatively, the register bit SC_I2CCMDFIN in the SC1_I2CSTAT can be used for waiting. To initiate a transmit segment, the data have to be written to the SC1_DATA data register, followed by setting the register bit SC_I2CSEND in the SC1_I2CCTRL1 register, and completed by waiting until it clears. Alternatively, the register bit SC_I2CTXFIN in the SC1_I2CSTAT can be used for waiting. A receive segment is initiated by setting the register bit SC_I2CRECV in the SC1_I2CCTRL1 register, waiting until it clears, and then reading from the SC1_DATA data register. Alternatively, the register bit SC_I2CRXFIN in the SC1_I2CSTAT can be used for waiting. Now the register bit SC_I2CRXNAK in the SC1_I2CSTAT register indicates if a NACK or ACK was received from an I2C slave device. Interrupts are generated on the following events: ● Bus command (SC_I2CSTART/SC_I2CSTOP) completed (0 to 1 transition of SC_I2CCMDFIN) ● Character transmitted and slave device responded with NACK ● Character transmitted (0 to 1 transition of SC_I2CTXFIN) ● Character received (0 to 1 transition of SC_I2CRXFIN) ● Received and lost character while receive FIFO was full (Receive overrun error) ● Transmitted character while transmit FIFO was empty (Transmit underrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC1CFG and INT_CFG registers must be enabled. 53/130 Functional description—application modules 7.2.4 SN250 Registers SC1_MODE [0x44AA] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 SC1_MODE SC1_MODE 0-RW 1 0-RW 0 SC1 Mode: 0 = disabled; 1 = UART mode; 2 = SPI mode; 3 = I2C mode. Note To change between modes, the previous mode must be disabled first. [1:0] SC1_DATA [0x449E] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC1_DATA 0-RW 7 SC1_DATA 0-RW 6 [7:0] 0-RW 5 0-RW 4 Transmit and receive data register. Writing to this register pushes a byte onto the transmit FIFO. Reading from this register pulls a byte from the receive FIFO. SC1_UARTPER [0x44B4] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 SC1_UARTPER SC1_UARTPER 0-RW 7 SC1_UARTPER 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 The baud rate period (N) of the clock rate as seen in the equation: 24MHz Rate = -------------------------------------------2 ⋅ ( N + ( 0.5 ⋅ F ) ) 54/130 SN250 Functional description—application modules SC1_UARTFRAC [0x44B6] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 SC1_ UARTFRAC 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 SC1_UARTFRAC [0] The baud rate fractional remainder (F) of the clock rate as derived from the equation: 24MHz Rate = -------------------------------------------2 ⋅ ( N + ( 0.5 ⋅ F ) ) SC1_UARTCFG [0x44AE] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 SC1_ UARTAUTO SC1_ UARTFLOW SC1_ UARTODD SC1_ UARTPAR SC1_ UART2STP SC1_ UART8BIT SC1_ UARTRTS 0-R 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC1_UARTAUTO [6] Set this bit to enable automatic nRTS assertion by hardware. nRTS will be deasserted when the UART can receive only one more character before the buffer is full. nRTS will be reasserted when the UART can receive more than one character before the buffer is full. The SC1_UARTRTS bit in this register has no effect when this bit is set. SC1_UARTFLOW [5] Set this bit to enable nRTS/nCTS signals. Clear this bit to disable the signals. When this bit is cleared, the nCTS signal is asserted in hardware to enable the UART transmitter. The GPIO_CFG register should be configured for mode SC1-4A for hardware handshake with nRTS/nCTS and SC1-2 for no handshaking. SC1_UARTODD [4] Clear this bit for even parity. Set this bit for odd parity. SC1_UARTPAR [3] Clear this bit for no parity. Set this bit for one parity bit. SC1_UART2STP [2] Clear this bit for one stop bit. Set this bit for two stop bits SC1_UART8BIT [1] Clear this bit for seven data bits. Set this bit for eight data bits. SC1_UARTRTS [0] RTS is an output signal. When this bit is set, the signal is asserted (== TTL logic 0, GPIO is low, 'XON', RS232 positive voltage), the transmission will proceed. When this bit is cleared, the signal is deasserted (== TTL logic 1, GPIO is high, 'XOFF', RS232 negative voltage), the transmission is inhibited. 55/130 Functional description—application modules SN250 SC1_UARTSTAT [0x44A4] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 SC1_ UARTTXIDLE SC1_ UARTPARERR SC1_ UARTFRMERR SC1_ UARTRXOVF SC1_ UARTTXFREE SC1_ UARTRXVAL SC1_ UARTCTS 0-R 7 1-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC1_UARTTXIDLE [6] This bit is set when the transmit FIFO is empty and the transmitter is idle. SC1_UARTPARERR [5] This bit is set when the receive FIFO has seen a parity error. This bit clears when the data register (SC1_DATA) is read. SC1_UARTFRMERR [4] This bit is set when the receive FIFO has seen a frame error. This bit clears when the data register (SC1_DATA) is read. SC1_UARTRXOVF [3] This bit is set when the receive FIFO has been overrun. This bit clears when the data register (SC1_DATA) is read. SC1_UARTTXFREE [2] This bit is set when the transmit FIFO is ready to accept at least one byte. SC1_UARTRXVAL [1] This bit is set when the receive FIFO contains at least one byte. SC1_UARTCTS [0] This bit shows the current state of the nCTS input signal at the nCTS pin (pin 19, GPIO11). When CTS = 1, the signal is asserted (== TTL logic 0, GPIO is low, 'XON', RS232 positive voltage), the transmission will proceed. When CTS = 0, the signal is deasserted (== TTL logic 1, GPIO is high, 'XOFF', RS232 negative voltage), transmission is inhibited at the end of the current character. Any characters in the transmit buffer will remain there. SC1_RATELIN [0x44B0] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 SC1_RATELIN [3:0] SC1_RATELIN 0-RW 3 0-RW 2 The linear component (LIN) of the clock rate as seen in the equation: 24MHz Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 56/130 0-RW 1 0-RW 0 SN250 Functional description—application modules SC1_RATEEXP [0x44B2] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 SC1_RATEEXP [3:0] SC1_RATEEXP 0-RW 3 0-RW 2 0-RW 1 0-RW 0 The exponential component (EXP) of the clock rate as seen in the equation: 24MHz Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 SC1_SPICFG [0x44AC] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 SC_ SPIRXDRV SC_SPIMST SC_SPIRPT SC_SPIORD SC_SPIPHA SC_SPIPOL 0-R 7 0-R 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_SPIRXDRV [5] Receiver-driven mode selection bit (SPI master mode only). Clearing this bit will initiate transactions when transmit data is available. Setting this bit will initiate transactions when the receive buffer (FIFO or DMA) has space. SC_SPIMST [4] This bit must always be set to put the SPI in master mode (slave mode is not valid). SC_SPIRPT [3] This bit controls behavior on a transmit buffer underrun condition in slave mode. Clearing this bit will send the BUSY token (0xFF) and setting this bit will repeat the last byte. Changing this bit will only take effect when the transmit FIFO is empty and the transmit serializer is idle. SC_SPIORD [2] Clearing this bit will result in the Most Significant Bit being transmitted first while setting this bit will result in the Least Significant Bit being transmitted first. SC_SPIPHA [1] Clock phase configuration is selected with clearing this bit for sampling on the leading (first edge) and setting this bit for sampling on second edge. SC_SPIPOL [0] Clock polarity configuration is selected with clearing this bit for a rising leading edge and setting this bit for a falling leading edge. 57/130 Functional description—application modules SN250 SC1_SPISTAT [0x44A0] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ SPITXIDLE SC_ SPITXFREE SC_ SPIRXVAL SC_ SPIRXOVF 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC_SPITXIDLE [3] This bit is set when the transmit FIFO is empty and the transmitter is idle. SC_SPITXFREE [2] This bit is set when the transmit FIFO is ready to accept at least one byte. SC_SPIRXVAL [1] This bit is set when the receive FIFO contains at least one byte. SC_SPIRXOVF [0] This bit is set when the receive FIFO has been overrun. This bit clears when the data register (SC1_DATA) is read. SC1_I2CCTRL1 [0x44A6] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ I2CSTOP SC_ I2CSTART SC_ I2CSEND SC_ I2CRECV 0-R 7 0-R 6 0-R 5 0-R 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_I2CSTOP [3] Setting this bit sends the STOP command. It auto clears when the command completes. SC_I2CSTART [2] Setting this bit sends the START or repeated START command. It autoclears when the command completes. SC_I2CSEND [1] Setting this bit transmits a byte. It autoclears when the command completes. SC_I2CRECV [0] Setting this bit receives a byte. It autoclears when the command completes. 58/130 SN250 Functional description—application modules SC1_I2CCTRL2 [0x44A8] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 SC_I2CACK 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 SC_I2CACK [0] Setting this bit will signal ACK after a received byte. Clearing this bit will signal NACK after a received byte. SC1_I2CSTAT [0x44A2] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ I2CCMDFIN SC_ I2CRXFIN SC_ I2CTXFIN SC_ I2CRXNAK 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC_I2CCMDFIN [3] This bit is set when a START or STOP command completes. It autoclears on next bus activity. SC_I2CRXFIN [2] This bit is set when a byte is received. It autoclears on next bus activity. SC_I2CTXFIN [1] This bit is set when a byte is transmitted. It autoclears on next bus activity. SC_I2CRXNAK [0] This bit is set when a NACK is received from the slave. It autoclears on next bus activity. 59/130 Functional description—application modules SN250 SC1_DMACTRL [0x4498] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 SC_ TXDMARST SC_ RXDMARST SC_TXLODB SC_TXLODA SC_RXLODB SC_RXLODA 0-R 7 0-R 6 0-W 5 0-W 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_TXDMARST [5] Setting this bit will reset the transmit DMA. The bit is autocleared. SC_RXDMARST [4] Setting this bit will reset the receive DMA. This bit is autocleared. SC_TXLODB [3] Setting this bit loads DMA transmit buffer B addresses and starts the DMA controller processing transmit buffer B. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer B is active or pending. Reading this bit as zero indicates DMA processing for buffer B is complete or idle. SC_TXLODA [2] Setting this bit loads DMA transmit buffer A addresses and starts the DMA controller processing transmit buffer A. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer A is active or pending. Reading this bit as zero indicates DMA processing for buffer A is complete or idle. SC_RXLODB [1] Setting this bit loads DMA receive buffer B addresses and starts the DMA controller processing receive buffer B. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer B is active or pending. Reading this bit as zero indicates DMA processing for buffer B is complete or idle. SC_RXLODA [0] Setting this bit loads DMA receive buffer A addresses and starts the DMA controller processing receive buffer A. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer A is active or pending. Reading this bit as zero indicates DMA processing for buffer A is complete or idle. 60/130 SN250 Functional description—application modules SC1_DMASTAT [0x4496] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 SC1_ RXFRMB SC1_ RXFRMA SC1_ RXPARB SC1_ RXPARA SC_RXOVFB SC_RXOVFA SC_TXACTB SC_TXACTA SC_RXACTB SC_RXACTA 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC1_RXFRMB [9] This bit is set when DMA receive buffer B was passed a frame error from the lower hardware FIFO. This bit is autocleared the next time buffer B is loaded or when the receive DMA is reset. SC1_RXFRMA [8] This bit is set when DMA receive buffer A was passed a frame error from the lower hardware FIFO. This bit is autocleared the next time buffer A is loaded or when the receive DMA is reset. SC1_RXPARB [7] This bit is set when DMA receive buffer B was passed a parity error from the lower hardware FIFO. This bit is autocleared the next time buffer B is loaded or when the receive DMA is reset. SC1_RXPARA [6] This bit is set when DMA receive buffer A was passed a parity error from the lower hardware FIFO. This bit is autocleared the next time buffer A is loaded or when the receive DMA is reset. SC_RXOVFB [5] This bit is set when DMA receive buffer B was passed an overrun error from the lower hardware FIFO. Neither receive buffers were capable of accepting any more bytes (unloaded), and the FIFO filled up. Buffer B was the next buffer to load, and when it drained the FIFO, the overrun error was passed up to the DMA and flagged with this bit. This bit is autocleared the next time buffer B is loaded or when the receive DMA is reset. SC_RXOVFA [4] This bit is set when DMA receive buffer A was passed an overrun error from the lower hardware FIFO. Neither receive buffers were capable of accepting any more bytes (unloaded), and the FIFO filled up. Buffer A was the next buffer to load, and when it drained the FIFO the overrun error was passed up to the DMA and flagged with this bit. This bit is autocleared the next time buffer A is loaded or when the receive DMA is reset. SC_TXACTB [3] This bit is set when DMA transmit buffer B is currently active. SC_TXACTA [2] This bit is set when DMA transmit buffer A is currently active. SC_RXACTB [1] This bit is set when DMA receive buffer B is currently active. SC_RXACTA [0] This bit is set when DMA receive buffer A is currently active. 61/130 Functional description—application modules SN250 SC1_RXCNTA [0x4490] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC1_RXCNTA SC1_RXCNTA 0-R 7 SC1_RXCNTA 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in DMA receive buffer A where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SC1_RXCNTB [0x4492] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC1_RXCNTB SC1_RXCNTB 0-R 7 SC1_RXCNTB 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in DMA receive buffer B where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SC1_TXCNT [0x4494] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC1_TXCNT SC1_TXCNT 0-R 7 SC1_TXCNT 62/130 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in the active (loaded) DMA transmit buffer where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SN250 Functional description—application modules SC1_RXBEGA [0x4480] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC1_RXBEGA SC1_RXBEGA 0-RW 7 SC1_RXBEGA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for receive buffer A. SC1_RXENDA [0x4482] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC1_RXENDA SC1_RXENDA 0-RW 7 SC1_RXENDA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for receive buffer A. SC1_RXBEGB [0x4484] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC1_RXBEGB SC1_RXBEGB 0-RW 7 SC1_RXBEGB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for receive buffer B. 63/130 Functional description—application modules SN250 SC1_RXENDB [0x4486] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC1_RXENDB SC1_RXENDB 0-RW 7 SC1_RXENDB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for receive buffer B. SC1_TXBEGA [0x4488] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC1_TXBEGA SC1_TXBEGA 0-RW 7 SC1_TXBEGA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for transmit buffer A. SC1_TXENDA [0x448A] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC1_TXENDA SC1_TXENDA 0-RW 7 SC1_TXENDA 64/130 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for transmit buffer A. SN250 Functional description—application modules SC1_TXBEGB [0x448C] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-R 8 0-R 0-R 1 0-R 0 SC1_TXBEGB SC1_TXBEGB 0-RW 7 SC1_TXBEGB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for transmit buffer B. SC1_TXENDB [0x448E] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC1_TXENDB SC1_TXENDB 0-RW 7 SC1_TXENDB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for transmit buffer B. SC1_RXERRA [0x449A] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R SC1_RXERRA SC1_RXERRA 0-R 7 SC1_RXERRA 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location of the first error in the DMA receive buffer A. If there is no error, it will hold the value zero. This register will not be updated by subsequent errors arriving in the DMA. The next error will only be recorded if the buffer unloads and is reloaded or the receive DMA is reset. 65/130 Functional description—application modules SN250 SC1_RXERRB [0x449C] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC1_RXERRB SC1_RXERRB 0-R 7 0-R 6 SC1_RXERRB [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location of the first error in the DMA receive buffer B. If there is no error, it will hold the value zero. This register will not be updated by subsequent errors arriving in the DMA. The next error will only be recorded if the buffer unloads and is reloaded or the receive DMA is reset. INT_SC1CFG [0x4624] 15 0-R 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 INT_ SC1PARERR INT_ SC1FRMERR INT_ SCTXULDB INT_ SCTXULDA INT_ SCRXULDB INT_ SCRXULDA INT_SCNAK INT_ SCCMDFIN INT_ SCTXFIN INT_ SCRXFIN INT_ SCTXUND INT_ SCRXOVF INT_ SCTXIDLE INT_ SCTXFREE INT_ SCRXVAL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_SC1PARERR [14] Parity error received (UART) interrupt enable. INT_SC1FRMERR [13] Frame error received (UART) interrupt enable. INT_SCTXULDB [12] DMA Tx buffer B unloaded interrupt enable. INT_SCTXULDA [11] DMA Tx buffer A unloaded interrupt enable. INT_SCRXULDB [10] DMA Rx buffer B unloaded interrupt enable. INT_SCRXULDA [9] DMA Rx buffer A unloaded interrupt enable. INT_SCNAK [8] Nack received (I2C) interrupt enable. INT_SCCMDFIN [7] START/STOP command complete (I2C) interrupt enable. INT_SCTXFIN [6] Transmit operation complete (I2C) interrupt enable. INT_SCRXFIN [5] Receive operation complete (I2C) interrupt enable. INT_SCTXUND [4] Transmit buffer underrun interrupt enable. INT_SCRXOVF [3] Receive buffer overrun interrupt enable. INT_SCTXIDLE [2] Transmitter idle interrupt enable. INT_SCTXFREE [1] Transmit buffer free interrupt enable. INT_SCRXVAL [0] Receive buffer has data interrupt enable. 66/130 SN250 Functional description—application modules INT_SC1FLAG [0x460C] 15 0-R 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 INT_ SC1PARERR INT_ SC1FRMERR INT_ SCTXULDB INT_ SCTXULDA INT_ SCRXULDB INT_ SCRXULDA INT_SCNAK INT_ SCCMDFIN INT_ SCTXFIN INT_ SCRXFIN INT_ SCTXUND INT_ SCRXOVF INT_ SCTXIDLE INT_ SCTXFREE INT_ SCRXVAL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_SC1PARERR [14] Parity error received (UART) interrupt pending. INT_SC1FRMERR [13] Frame error received (UART) interrupt pending. INT_SCTXULDB [12] DMA Tx buffer B unloaded interrupt pending. INT_SCTXULDA [11] DMA Tx buffer A unloaded interrupt pending. INT_SCRXULDB [10] DMA Rx buffer B unloaded interrupt pending. INT_SCRXULDA [9] DMA Rx buffer A unloaded interrupt pending. INT_SCNAK [8] Nack received (I2C) interrupt pending. INT_SCCMDFIN [7] START/STOP command complete (I2C) interrupt pending. INT_SCTXFIN [6] Transmit operation complete (I2C) interrupt pending. INT_SCRXFIN [5] Receive operation complete (I2C) interrupt pending. INT_SCTXUND [4] Transmit buffer underrun interrupt pending. INT_SCRXOVF [3] Receive buffer overrun interrupt pending. INT_SCTXIDLE [2] Transmitter idle interrupt pending. INT_SCTXFREE [1] Transmit buffer free interrupt pending. INT_SCRXVAL [0] Receive buffer has data interrupt pending. 67/130 Functional description—application modules 7.3 SN250 Serial controller SC2 The SN250 SC2 module provides synchronous (SPI or I2C) serial communications. Figure 8 is a block diagram of the SC2 module. Figure 8. SC2 block diagram The full-duplex interface of the SC2 module can be configured into one of these two communication modes, but it cannot run them simultaneously. To reduce the interrupt service requirements of the CPU, the SC2 module contains buffered data management schemes. A dedicated, buffered DMA controller is available to the SPI while a FIFO is available to both modes. In addition, a SC2 data register allows the software application direct access to the SC2 data. Finally, the SC2 routes the interface signals to GPIO pins. These are shared with other functions and are controlled by the GPIO_CFG register. For selecting alternate pin-functions, please refer to Table 17 and Table 18. 68/130 SN250 7.3.1 Functional description—application modules SPI modes The SPI mode of the SC2 supports both master and slave modes. It has a fixed word length of 8 bits. The SC2 SPI controller is enabled with SC2_MODE set to 2. The SC2 SPI mode has the following features: ● Master and slave modes ● Full duplex operation ● Programmable master mode clock frequency (12MHz max.) ● Slave mode up to 5MHz bit rate ● Programmable clock polarity and clock phase ● Selectable data shift direction (either LSB or MSB first) ● Optional slave select input The following signals can be made available on the GPIO pins: ● MOSI (master out/slave in) ● MISO (master in/slave out) ● MSCLK (serial clock) ● nSSEL (slave select—only in slave mode) SPI master mode The SC2 SPI Master controller is enabled with the SC_SPIMST set in the SC2_SPICFG register. The SC2 SPI module obtains its reference clock from a programmable clock generator. Clock rates are set by a clock division ratio from the 24 MHz clock: 24MHz Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 EXP is written to the SC2_RATEEXP register and LIN to the SC2_RATELIN register. Since the range for both values is 0 to 15, the fastest data rate is 12Mbps and the slowest is 22.9bps. The SC2 SPI Master supports various frame formats depending upon the clock polarity (SC_SPIPOL), clock phase (SC_SPIPHA), and direction of data (SC_SPIORD) (see Table 24). The register bits SC_SPIPOL, SC_SPIPHA, and SC_SPIORD are defined within the SC2_SPICFG register. Note: Switching the SPI configuration from SC_SPIPOL=1 to SC_SPIPOL=0 without subsequently setting SC2_MODE=0 and reinitializing the SPI will cause an extra byte (0xFE) to be transmitted immediately before the first intended byte. 69/130 Functional description—application modules SC2 SPI master mode formats SC2_MODE SC_SPIMST SC_SPIORD SC_SPIPHA SC_SPIPOL SC2_SPICFG GPIO_CFG[7:4] Table 24. SN250 2 1 0 0 0 SC2-3M mode 2 1 0 0 1 SC2-3M mode 2 1 0 1 0 SC2-3M mode 2 1 0 1 1 SC2-3M mode 2 1 1 - - SC2-3M mode Same as above except LSB first instead of MSB first 2 1 - - - SC2-4S mode Illegal 2 1 - - - SC2-2 mode Illegal Frame Format Serialized SC2 SPI transmit data is driven to the output pin MOSI. SC2 SPI master data is received from the input pin MISO. To generate slave select signals to SPI slave devices, other GPIO pins have to be used and their assertion must be controlled by software. Characters transmitted and received are passed through transmit and receive FIFOs. The transmit and receive FIFOs are 4 bytes deep. These FIFOs are accessed under software control by accessing the SC2_DATA data register or under hardware control using a DMA controller. When a transmit character is written to the (empty) transmit FIFO, the register bit SC_SPITXIDLE in the SC2_SPISTAT register clears and indicates that not all characters are transmitted yet. Further transmit characters can be written to the transmit FIFO until it is full, which causes the register bit SC_SPITXFREE in the SC2_SPISTAT register to clear. After shifting out one transmit character to the MOSI pin, space for one transmit character becomes available in the transmit FIFO. This causes the register bit SC_SPITXFREE in the SC2_SPISTAT register to get set. After all characters are shifted out, the transmit FIFO empties, which causes the register bit SC_SPITXIDLE in the SC2_SPISTAT register to get set also. Any character received is stored in the (empty) receive FIFO. The register bit SC_SPIRXVAL in the SC2_SPISTAT register is set to indicate that not all received characters are read out from receive FIFO. If software or DMA is not reading from the receive FIFO, the receive FIFO will store up to 4 characters. Any further reception is dropped and the register bit 70/130 SN250 Functional description—application modules SC_SPIRXOVF in the SC2_SPISTAT register is set. The RX FIFO hardware generates the INT_SCRXOVF interrupt, but the DMA register will not indicate the error condition until the RX FIFO is drained. Once the DMA marks a RX error, there are two conditions that will clear the error indication: setting the appropriate SC_TX/RXDMARST bit in the SC2_DMACTRL register, or loading the appropriate DMA buffer after it has unloaded. Receiving a character always requires transmitting a character. In a case when a long stream of receive characters is expected, a long sequence of (dummy) transmit characters must be generated. To avoid software or transmit DMA initiating these transfers (and consuming unnecessary bandwidth), the SPI serializer can be instructed to retransmit the last transmitted character or to transmit a busy token (0xFF), which is determined by the register bit SC_SPIRPT in the SC2_SPICFG register. This functionality can only be enabled (or disabled) when the transmit FIFO is empty and the transmit serializer is idle, as indicated by a cleared SC_SPITXIDLE register bit in the SC2_SPISTAT register. Every time an automatic character transmission is started, a transmit underrun is detected (as there is no data in transmit FIFO) and the register bit INT_SCTXUND in the INT_SC2FLAG register is set. Note that after disabling the automatic character transmission, the reception of new characters stops and the receive FIFO holds characters just received. Note: The event Receive DMA complete event does not automatically mean receive FIFO empty. Interrupts are generated by one of the following events: ● Transmit FIFO empty and last character shifted out (0 to 1 transition of SC_SPITXIDLE) ● Transmit FIFO changed from full to not full (0 to 1 transition of SC_SPITXFREE) ● Receive FIFO changed from empty to not empty (0 to 1 transition of SC_SPIRXVAL) ● Transmit DMA buffer A/B complete (1 to 0 transition of SC_TXACTA/B) ● Receive DMA buffer A/B complete (1 to 0 transition of SC_RXACTA/B) ● Received and lost character while receive FIFO was full (Receive overrun error) ● Transmitted character while transmit FIFO was empty (Transmit underrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC2CFG and INT_CFG register must be enabled. SPI slave mode The SC2 SPI Slave controller is enabled with the SC_SPIMST cleared in the SC2_SPICFG register. The SC2 SPI Slave controller receives its clock from an external SPI master device and supports rates up to 5Mbps. The SC2 SPI Slave supports various frame formats depending upon the clock polarity (SC_SPIPOL), clock phase (SC_SPIPHA), and direction of data (SC_SPIORD) (see Table 25). The register bits SC_SPIPOL, SC_SPIPHA, and SC_SPIORD are defined within the SC2_SPICFG registers. Note: Switching the SPI configuration from SC_SPIPOL=1 to SC_SPIPOL=0 without subsequently setting SC2_MODE=0 and reinitializing the SPI will cause an extra byte (0xFE) to be transmitted immediately before the first intended byte. 71/130 Functional description—application modules SC2 SPI slave formats SC2_MODE SC_SPIMST SC_SPIORD SC_SPIPHA SC_SPIPOL SC2_SPICFG GPIO_CFG[7:4] Table 25. SN250 2 0 0 0 0 SC2-4S mode 2 0 0 0 1 SC2-4S mode 2 0 0 1 0 SC2-4S mode 2 0 0 1 1 SC2-4S mode 2 0 1 - - SC2-4S Same as above except LSB first instead of MSB first mode 2 0 - - - SC23M mode Illegal 2 0 - - - SC2-2 mode Illegal Frame Format When the slave select (nSSEL) signal is asserted (by the Master), SC2 SPI transmit data is driven to the output pin MISO and SC2 SPI data is received from the input pin MOSI. The slave select signal nSSEL is used to enable driving the serialized data output signal MISO. It is also used to reset the SC2 SPI slave shift register. Characters received and transmitted are passed through receive and transmit FIFOs. The transmit and receive FIFOs are 4 bytes deep. These FIFOs are accessed under software control by accessing the SC2_DATA data register or under hardware control using a DMA controller. Any character received is stored in the (empty) receive FIFO. The register bit SC_SPIRXVAL in the SC2_SPISTAT register is set to indicate that not all received characters are read out from receive FIFO. If software or DMA is not reading from the receive FIFO, the receive FIFO will store up to 4 characters. Any further reception is dropped, and the register bit SC_SPIRXOVF in the SC2_SPISTAT register is set. The RX FIFO hardware generates the 72/130 SN250 Functional description—application modules INT_SCRXOVF interrupt, but the DMA register will not indicate the error condition until the RX FIFO is drained. Once the DMA marks a RX error, there are two conditions that will clear the error indication: setting the appropriate SC_TX/RXDMARST bit in the SC2_DMACTRL register, or loading the appropriate DMA buffer after it has unloaded. Receiving a character always causes a serialization of a transmit character pulled from the transmit FIFO. When the transmit FIFO is empty, a transmit underrun is detected (no data in transmit FIFO) and the register bit INT_SCTXUND in the INT_SC2FLAG register is set. Because there is no character available for serialization, the SPI serializer retransmits the last transmitted character or a busy token (0xFF), which is determined by the register bit SC_SPIRPT in the SC2_SPICFG register. Note: Even during a transmit underrun, the register bit SC_SPITXIDLE in the SC2_SPISTAT register will clear when the SPI master begins to clock data out of the MISO pin, indicating the transmitter is not idle. After a complete byte has been clocked out, the bit SC_SPITXIDLE will be set and the register bit INT_SCTXIDLE in the INT_SC2FLAG interrupt register will be set. The bits SC_SPITXIDLE and INT_SCTXIDLE will toggle in this manner for every byte that is transmitted as an underrun. When a transmit character is written to the (empty) transmit FIFO, the SC2_SPISTAT register and the INT_SC2FLAG register do not change. Further transmit characters can be written to the transmit FIFO until it is full, which causes the register bit SC_SPITXFREE in the SC2_SPISTAT register to clear. When the SPI master begins to clock data out of the MISO pin, the register bit SC_SPITXIDLE in the SC2_SPISTAT register clears (after the first bit is clocked out) and indicates that not all characters are transmitted yet. After shifting one transmit character to the MISO pin, space for one transmit character becomes available in the transmit FIFO. This causes the register bit SC_SPITXFREE in the SC2_SPISTAT register to be set. After all characters are shifted out, the transmit FIFO is empty, which causes the register bit SC_SPITXIDLE in the SC2_SPISTAT register to be set. The SPI Slave controller must guarantee that there is time to move new transmit data from the transmit FIFO into the hardware serializer. To provide sufficient time, the SPI Slave controller inserts a byte of padding onto the start of every new string of transmit data. After slave select asserts and the bit SC_SPIRXVAL in the SC2SPISTAT register gets set at least once, the following operation will hold true until slave select deasserts. Whenever the transmit FIFO is empty and data is placed into the transmit FIFO, either manually or placed through DMA, the SPI hardware will insert an extra byte onto the front of the transmission as if this byte was placed there by software. The value of the byte that is inserted is chosen by the bit SC_SPIRPT in the SC2_SPICFG. Take note that when this extra byte is transmitted, the bit INT_SCTXUND will get set in the INT_SC2FLAG register. Interrupts are generated by one of the following events: ● Transmit FIFO empty and last character shifted out (0 to 1 transition of SC_SPITXIDLE) ● Transmit FIFO changed from full to not full (0 to 1 transition of SC_SPITXFREE) ● Receive FIFO changed from empty to not empty (0 to 1 transition of SC_SPIRXVAL) ● Transmit DMA buffer A/B complete (1 to 0 transition of SC_TXACTA/B) ● Receive DMA buffer A/B complete (1 to 0 transition of SC_RXACTA/B) ● Received and lost character while receive FIFO was full (Receive overrun error) ● Transmitted character while transmit FIFO was empty (Transmit underrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC2CFG and INT_CFG register must be enabled. 73/130 Functional description—application modules 7.3.2 SN250 I2C Master Mode The SC2 I2C controller is only available in master mode. The SC2 I2C controller is enabled with SC2_MODE set to 3. The I2C Master controller supports Standard (100 Kbps) and Fast (400 Kbps) I2C modes. Address arbitration is not implemented, so multiple master applications are not supported. The I2C signals are pure open-collector signals, and external pull-up resistors are required. The SC2 I2C mode has the following features: ● Programmable clock frequency (400kHz max.) ● 7- and 10-bit addressing The following signals can be made available on the GPIO pins: ● SDA (serial data) ● SCL (serial clock) The I2C Master controller obtains its reference clock from a programmable clock generator. Clock rates are set by a clock division ratio from the 24MHz clock: 24MHz Nominal Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 EXP is written to the SC2_RATEEXP register and LIN to the SC2_RATELIN register. Table 26 shows the rate settings for Standard I2C (100 Kbps) and Fast I2C (400 Kbps) operation. Table 26. I2C nominal rate programming Nominal Rate SPPR SPR 100 Kbps 14 3 375 Kbps 15 1 400 Kbps 14 1 Note that, at 400 Kbps, the I2C specification requires the minimum low period of SCL to be 1.3µs. To be strictly I2C compliant, the rate needs to be lowered to 375 Kbps. The I2C Master controller supports generation of various frame segments defined by the register bits SC_I2CSTART, SC_I2CSTOP, SC_I2CSEND, and SC_I2CRECV within the SC2_I2CCTRL1 register. Table 27 summarizes these frames. Full I2C frames have to be constructed under software control by generating individual I2C segments. All necessary segment transitions are shown in Figure 7. ACK or NACK generation of an I2C receive frame segment is determined with the register bit SC_I2CACK in the SC2_I2CCTRL2 register. Generation of a 7-bit address is accomplished with one transmit segment. The upper 7 bits of the transmitted character contain the 7-bit address. The remaining lower bit contains the command type (“read” or “write”). Generation of a 10-bit address is accomplished with two transmit segments. The upper 5 bits of the first transmit character must be set to 0x1E. The next 2 bits are for the 2 most significant bits of the 10-bit address. The remaining lower bit contains the command type (“read” or “write”). The second transmit segment is for the remaining 8 bits of the 10-bit address. 74/130 SN250 Functional description—application modules Table 27. I2C master segment formats SC2_MODE SC_I2CSTART SC_I2CSEND SC_I2CRECV SC_I2CSTOP GPIO_CFG[7:4] SC2_I2CCTR L1 3 1 0 0 0 SC2-2 mode 3 0 1 0 0 SC2-2 mode 3 0 0 1 0 SC2-2 mode 3 0 0 0 1 SC2-2 mode 3 0 0 0 0 SC2-2 mode No pending frame segment 3 1 1 1 1 - 1 1 - 1 1 SC2-2 mode Illegal 3 - - - - SC2-4M mode Illegal 3 - - - - SC2-4A mode Illegal Frame Segments 75/130 Functional description—application modules SN250 Characters received and transmitted are passed through receive and transmit FIFOs. The SC2 I2C master transmit and receive FIFOs are 1 byte deep. These FIFOs are accessed under software control. (Re)start and stop segments are initiated by setting the register bits SC_I2CSTART or SC_I2CSTOP in the SC2_I2CCTRL1 register, followed by waiting until they have cleared. Alternatively, the register bit SC_I2CCMDFIN in the SC2_I2CSTAT can be used for waiting. For initiating a transmit segment, the data has to be written to the SC2_DATA data register, followed by setting the register bit SC_I2CSEND in the SC2_I2CCTRL1 register, and completed by waiting until it clears. Alternatively, the register bit SC_I2CTXFIN in the SC2_I2CSTAT can be used for waiting. A receive segment is initiated by setting the register bit SC_I2CRECV in the SC2_I2CCTRL1 register, waiting until it clears, and then reading from the SC2_DATA data register. Alternatively, the register bit SC_I2CRXFIN in the SC2_I2CSTAT can be used for waiting. Now the register bit SC_I2CRXNAK in the SC2_I2CSTAT register indicates if a NACK or ACK was received from an I2C slave device. Interrupts are generated on the following events: ● Bus command (SC_I2CSTART/SC_I2CSTOP) completed (0 to 1 transition of SC_I2CCMDFIN) ● Character transmitted and slave device responded with NACK ● Character transmitted (0 to 1 transition of SC_I2CTXFIN) ● Character received (0 to 1 transition of SC_I2CRXFIN) ● Received and lost character while receive FIFO was full (Receive overrun error) ● Transmitted character while transmit FIFO was empty (Transmit underrun error) To generate interrupts to the CPU, the interrupt masks in the INT_SC2CFG and INT_CFG register must be enabled. 76/130 SN250 7.3.3 Functional description—application modules Registers SC2_MODE [0x442A] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 SC2_MODE [1:0] SC2_MODE 0-RW 1 0-RW 0 SC2 Mode: 0 = disabled; 1 = disabled; 2 = SPI mode; 3 = I2C mode. Note: To change between modes, the previous mode must be disabled first. SC2_DATA [0x441E] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC2_DATA 0-RW 7 SC2_DATA 0-RW 6 [7:0] 0-RW 5 0-RW 4 Transmit and receive data register. Writing to this register pushes a byte onto the transmit FIFO. Reading from this register pulls a byte from the receive FIFO. SC2_RATELIN [0x4430] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 SC2_RATELIN [3:0] SC2_RATELIN 0-RW 3 0-RW 2 0-RW 1 0-RW 0 The linear component (LIN) of the clock rate as seen in the equation: 24MHz Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 77/130 Functional description—application modules SN250 SC2_RATEEXP [0x4432] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0-R 7 0-R 6 0-R 5 0-R 4 SC2_RATEEXP [3:0] SC2_RATEEXP 0-RW 3 0-RW 2 0-RW 1 0-RW 0 The exponential component (EXP) of the clock rate as seen in the equation: 24MHz Rate = ------------------------------------------------EXP 2 ⋅ ( LIN + 1 ) ⋅ 2 SC2_SPICFG [0x442C] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 SC_ SPIRXDRV 0-R 7 0-R 6 0-RW 5 SC_SPIMST SC_SPIRPT SC_SPIORD SC_SPIPHA SC_SPIPOL 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_SPIRXDRV [5] Receiver-driven mode selection bit (SPI master mode only). Clearing this bit will initiate transactions when transmit data is available. Setting this bit will initiate transactions when the receive buffer (FIFO or DMA) has space. SC_SPIMST [4] Setting this bit will put the SPI in master mode while clearing this bit will put the SPI in slave mode. SC_SPIRPT [3] This bit controls behavior on a transmit buffer underrun condition in slave mode. Clearing this bit will send the BUSY token (0xFF) and setting this bit will repeat the last byte. Changing this bit will only take effect when the transmit FIFO is empty and the transmit serializer is idle. SC_SPIORD [2] Clearing this bit will result in the Most Significant Bit being transmitted first while setting this bit will result in the Least Significant Bit being transmitted first. SC_SPIPHA [1] Clock phase configuration is selected with clearing this bit for sampling on the leading (first edge) and setting this bit for sampling on second edge. SC_SPIPOL [0] Clock polarity configuration is selected with clearing this bit for a rising leading edge and setting this bit for a falling leading edge. 78/130 SN250 Functional description—application modules SC2_SPISTAT [0x4420] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ SPITXIDLE SC_ SPITXFREE SC_ SPIRXVAL SC_ SPIRXOVF 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC_SPITXIDLE [3] This bit is set when the transmit FIFO is empty and the transmitter is idle. SC_SPITXFREE [2] This bit is set when the transmit FIFO is ready to accept at least one byte. SC_SPIRXVAL [1] This bit is set when the receive FIFO contains at least one byte. SC_SPIRXOVF [0] This bit is set when the receive FIFO has been overrun. This bit clears when the data register (SC2_DATA) is read. SC2_I2CCTRL1 [0x4426] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ I2CSTOP SC_ I2CSTART SC_ I2CSEND SC_ I2CRECV 0-R 7 0-R 6 0-R 5 0-R 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_I2CSTOP [3] Setting this bit sends the STOP command. It autoclears when the command completes. SC_I2CSTART [2] Setting this bit sends the START or repeated START command. It autoclears when the command completes. SC_I2CSEND [1] Setting this bit transmits a byte. It autoclears when the command completes. SC_I2CRECV [0] Setting this bit receives a byte. It autoclears when the command completes. 79/130 Functional description—application modules SN250 SC2_I2CCTRL2 [0x4428] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 SC_I2CACK 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-RW 0 SC_I2CACK [0] Setting this bit will signal ACK after a received byte. Clearing this bit will signal NACK after a received byte. SC2_I2CSTAT [0x4422] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 0 0 SC_ I2CCMDFIN SC_ I2CRXFIN SC_ I2CTXFIN SC_ I2CRXNAK 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC_I2CCMDFIN [3] This bit is set when a START or STOP command completes. It autoclears on next bus activity. SC_I2CRXFIN [2] This bit is set when a byte is received. It autoclears on next bus activity. SC_I2CTXFIN [1] This bit is set when a byte is transmitted. It autoclears on next bus activity. SC_I2CRXNAK [0] This bit is set when a NACK is received from the slave. It autoclears on next bus activity. 80/130 SN250 Functional description—application modules SC2_DMACTRL [0x4418] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 SC_ TXDMARST SC_ RXDMARST SC_TXLODB SC_TXLODA SC_RXLODB SC_RXLODA 0-R 7 0-R 6 0-W 5 0-W 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 SC_TXDMARST [5] Setting this bit will reset the transmit DMA. The bit is autocleared. SC_RXDMARST [4] Setting this bit will reset the receive DMA. This bit is autocleared. SC_TXLODB [3] Setting this bit loads DMA transmit buffer B addresses and starts the DMA controller processing transmit buffer B. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer B is active or pending. Reading this bit as zero indicates DMA processing for buffer B is complete or idle. SC_TXLODA [2] Setting this bit loads DMA transmit buffer A addresses and starts the DMA controller processing transmit buffer A. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer A is active or pending. Reading this bit as zero indicates DMA processing for buffer A is complete or idle. SC_RXLODB [1] Setting this bit loads DMA receive buffer B addresses and starts the DMA controller processing receive buffer B. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer B is active or pending. Reading this bit as zero indicates DMA processing for buffer B is complete or idle. SC_RXLODA [0] Setting this bit loads DMA receive buffer A addresses and starts the DMA controller processing receive buffer A. This bit is autocleared when DMA completes. Writing a zero to this bit will not have any effect. Reading this bit as one indicates DMA processing for buffer A is active or pending. Reading this bit as zero indicates DMA processing for buffer A is complete or idle. 81/130 Functional description—application modules SN250 SC2_DMASTAT [0x4416] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0 0 0 0 0 0 0 0 0 0 SC_RXOVFB SC_RXOVFA SC_TXACTB SC_TXACTA SC_RXACTB SC_RXACTA 0-R 7 0-R 6 0-R 5 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 SC_RXOVFB [5] This bit is set when DMA receive buffer B was passed an overrun error from the lower hardware FIFO. Neither receive buffers were capable of accepting any more bytes (unloaded), and the FIFO filled up. Buffer B was the next buffer to load, and when it drained the FIFO the overrun error was passed up to the DMA and flagged with this bit. This bit is autocleared the next time buffer B is loaded or when the receive DMA is reset. SC_RXOVFA [4] This bit is set when DMA receive buffer A was passed an overrun error from the lower hardware FIFO. Neither receive buffers were capable of accepting any more bytes (unloaded), and the FIFO filled up. Buffer A was the next buffer to load, and when it drained the FIFO the overrun error was passed up to the DMA and flagged with this bit. This bit is autocleared the next time buffer A is loaded or when the receive DMA is reset. SC_TXACTB [3] This bit is set when DMA transmit buffer B is currently active. SC_TXACTA [2] This bit is set when DMA transmit buffer A is currently active. SC_RXACTB [1] This bit is set when DMA receive buffer B is currently active. SC_RXACTA [0] This bit is set when DMA receive buffer A is currently active. SC2_RXCNTA [0x4410] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC2_RXCNTA SC2_RXCNTA 0-R 7 SC2_RXCNTA 82/130 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in DMA receive buffer A where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SN250 Functional description—application modules SC2_RXCNTB [0x4412] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC2_RXCNTB SC2_RXCNTB 0-R 7 SC2_RXCNTB 0-R 6 0-R 5 [12:0] 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in DMA receive buffer B where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SC2_TXCNT [0x4414] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC2_TXCNT SC2_TXCNT 0-R 7 0-R 6 SC2_TXCNT 0-R 5 [12:0] 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location in the active (loaded) DMA transmit buffer where the next byte will be placed. When the buffer fills and subsequently unloads, this register wraps around and holds the value zero (pointing back to the first location in the buffer). SC2_RXBEGA [0x4400] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC2_RXBEGA SC2_RXBEGA 0-RW 7 SC2_RXBEGA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for receive buffer A. 83/130 Functional description—application modules SN250 SC2_RXENDA [0x4402] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC2_RXENDA SC2_RXENDA 0-RW 7 SC2_RXENDA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for receive buffer A. SC2_RXBEGB [0x4404] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC2_RXBEGB SC2_RXBEGB 0-RW 7 SC2_RXBEGB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for receive buffer B. SC2_RXENDB [0x4406] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC2_RXENDB SC2_RXENDB 0-RW 7 SC2_RXENDB 84/130 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for receive buffer B. SN250 Functional description—application modules SC2_TXBEGA [0x4408] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC2_TXBEGA SC2_TXBEGA 0-RW 7 SC2_TXBEGA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for transmit buffer A. SC2_TXENDA [0x440A] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC2_TXENDA SC2_TXENDA 0-RW 7 SC2_TXENDA 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for transmit buffer A. SC2_TXBEGB [0x440C] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW SC2_TXBEGB SC2_TXBEGB 0-RW 7 SC2_TXBEGB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA Start address (byte aligned) for transmit buffer B. 85/130 Functional description—application modules SN250 SC2_TXENDB [0x440E] 15 0-R 14 1-R 13 1-R 0 1 1 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 1 0-RW 0 SC2_TXENDB SC2_TXENDB 0-RW 7 SC2_TXENDB 0-RW 6 [12:0] 0-RW 5 0-RW 4 0-RW 3 0-RW 2 DMA End address (byte aligned) for transmit buffer B. SC2_RXERRA [0x441A] 15 14 13 12 11 10 9 8 0-R 0-R 0-R 0-R 0-R 0-R 0-R 0-R 0 0 0 SC2_RXERRA SC2_RXERRA 0-R 0-R 0-R 0-R 0-R 0-R 0-R 0-R 7 6 5 4 3 2 1 0 SC2_RXERRA [12:0] A byte offset (from 0) which points to the location of the first error in the DMA receive buffer A. If there is no error, it will hold the value zero. This register will not be updated by subsequent errors arriving in the DMA. The next error will only be recorded if the buffer unloads and is reloaded or the receive DMA is reset. SC2_RXERRB [0x441C] 15 0-R 14 0-R 13 0-R 0 0 0 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 1 0-R 0 SC2_RXERRB SC2_RXERRB 0-R 7 SC2_RXERRB 86/130 0-R 6 [12:0] 0-R 5 0-R 4 0-R 3 0-R 2 A byte offset (from 0) which points to the location of the first error in the DMA receive buffer B. If there is no error, it will hold the value zero. This register will not be updated by subsequent errors arriving in the DMA. The next error will only be recorded if the buffer unloads and is reloaded or the receive DMA is reset. SN250 Functional description—application modules INT_SC2CFG [0x4626] 15 0-R 14 0-R 13 0-R 12 0-RW 11 0-RW 10 0-RW 0 0 0 INT_ SCTXULDB INT_ SCTXULDA INT_ INT_ INT_SCNAK SCRXULDB SCRXULDA INT_ SCCMDFIN INT_ SCTXFIN INT_ SCRXFIN INT_ SCTXUND INT_ SCRXOVF INT_ SCTXIDLE INT_ SCTXFREE INT_ SCRXVAL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_SCTXULDB [12] DMA Tx buffer B unloaded interrupt enable. INT_SCTXULDA [11] DMA Tx buffer A unloaded interrupt enable. INT_SCRXULDB [10] DMA Rx buffer B unloaded interrupt enable. INT_SCRXULDA [9] DMA Rx buffer A unloaded interrupt enable. INT_SCNAK [8] Nack received (I2C) interrupt enable. INT_SCCMDFIN [7] START/STOP command complete (I2C) interrupt enable. INT_SCTXFIN [6] Transmit operation complete (I2C) interrupt enable. INT_SCRXFIN [5] Receive operation complete (I2C) interrupt enable. INT_SCTXUND [4] Transmit buffer underrun interrupt enable. INT_SCRXOVF [3] Receive buffer overrun interrupt enable. INT_SCTXIDLE [2] Transmitter idle interrupt enable. INT_SCTXFREE [1] Transmit buffer free interrupt enable. INT_SCRXVAL [0] Receive buffer has data interrupt enable. 9 0-RW 8 0-RW 87/130 Functional description—application modules SN250 INT_SC2FLAG [0x460E] 15 0-R 14 0-R 13 0-R 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 0 0 INT_ SCTXULDB INT_ SCTXULDA INT_ SCRXULDB INT_ SCRXULDA INT_SCNAK INT_ SCCMDFIN INT_ SCTXFIN INT_ SCRXFIN INT_ SCTXUND INT_ SCRXOVF INT_ SCTXIDLE INT_ SCTXFREE INT_ SCRXVAL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_SCTXULDB [12] DMA Tx buffer B unloaded interrupt pending. INT_SCTXULDA [11] DMA Tx buffer A unloaded interrupt pending. INT_SCRXULDB [10] DMA Rx buffer B unloaded interrupt pending. INT_SCRXULDA [9] DMA Rx buffer A unloaded interrupt pending. INT_SCNAK [8] Nack received (I2C) interrupt pending. INT_SCCMDFIN [7] START/STOP command complete (I2C) interrupt pending. INT_SCTXFIN [6] Transmit operation complete (I2C) interrupt pending. INT_SCRXFIN [5] Receive operation complete (I2C) interrupt pending. INT_SCTXUND [4] Transmit buffer underrun interrupt pending. INT_SCRXOVF [3] Receive buffer overrun interrupt pending. INT_SCTXIDLE [2] Transmitter idle interrupt pending. INT_SCTXFREE [1] Transmit buffer free interrupt pending. INT_SCRXVAL [0] Receive buffer has data interrupt pending. 88/130 SN250 7.4 Functional description—application modules General purpose timers The SN250 integrates two general-purpose, 16-bit timers—TMR1 and TMR2. Each of the two timers contains the following features: ● Configurable clock source ● Counter load ● Two output compare registers ● Two input capture registers ● Can be configured to do PWM ● Up/down counting (for PWM motor drive phase correction) ● Single shot operation mode (timer stops at zero or threshold) Figure 9 is a block diagram of the Timer TMR1 module. Timer TMR2 is identical. Figure 9. 7.4.1 Timer TMR1 block diagram Clock sources The clock source for each timer can be chosen from the main 12MHz clock, 32.768kHz clock, 1kHz RC-Clock, or from an external source (up to 100kHz) through TMR1CLK or TMR2CLK. After choosing the clock source (see Table 28), the frequency can be further divided to generate the final timer cycle provided to the timer controller (see Table 29). In addition, the clock edge (either rising or falling) for this timer clock can be selected (see Table 30). 89/130 Functional description—application modules Table 28. Clock Source 0 1 kHz RC clock 1 32.768kHz clock 2 12 MHz clock 3 GPIO clock input Clock source divider settings TMR_PSCL[3:0] Clock Source Prescale Factor N = 0..10 2N N = 11..15 210 Table 30. Note: TMR1 and TMR2 clock source settings TMR_CLK[1:0] Table 29. SN250 Clock edge setting TMR_EDGE Clock Source 0 Rising 1 Falling All configuration changes do not take effect until the next edge of the timer's clock source. These functions are separately controlled for TMR1 and TMR2 by setting the bits TMR_CLK, TMR_FILT, TMR_EDGE, and TMR_PSCL in the timer registers TMR1_CFG and TMR2_CFG, respectively. 7.4.2 Timer functionality (counting) Each timer supports three counting modes: increasing, decreasing, or alternating (where the counting will increase, then decrease, then increase). These modes are controlled by setting the TMR_DOWN and TMR_BIDIR bits within the TMR1_CFG or TMR2_CFG registers. Upward counting continues until the counter value reaches the threshold value stored in the TMR1_TOP or TMR2_TOP register. Downward counting continues until the counter value reaches the value zero. When the alternating counting mode is enabled, a triangular-shaped waveform of the count-value can be created. Figure 10 through Figure 13 illustrate the different counting modes available from the timers. Counting can be enabled and disabled with the register bit TMR_EN in the TMR1_CFG or TMR2_CFG registers. When the timer is disabled, the counter stops counting and maintains its count value. Enabling can be masked with the pin TMR1ENMSK or TMR2ENMSK, depending on register bit TMR_EXTEN in the TMR1_CFG or TMR2_CFG registers. By default, the counting operation is repetitive. It can be restricted to single counting enabled with the register bit TMR_1SHOT located in the TMR1_CFG or TMR2_CFG registers. 90/130 SN250 Functional description—application modules Figure 10. Timer counting mode—saw tooth, up 91/130 Functional description—application modules Figure 11. Timer counting mode—saw tooth, down 92/130 SN250 SN250 Functional description—application modules Figure 12. Timer counting mode—alternating, initially up 93/130 Functional description—application modules Figure 13. Timer counting mode—alternating, initially down 94/130 SN250 SN250 7.4.3 Functional description—application modules Timer functionality (output compare) There are two output signals from each timer to generate application-specific waveforms. These waveforms are generated or altered by comparison results with the timer count value. There are four comparison results: ● Counter value reaches zero. ● Counter value reaches threshold value of TMR1_TOP or TMR2_TOP register. ● Counter value reaches comparison value of TMR1_CMPA or TMR2_CMPA register. ● Counter value reaches comparison value of TMR1_CMPB or TMR2_CMPB register. The output waveform generation from each timer is controlled with the register bits (TMR_CMPMOD or inverted with TMR_CMPINV) in the TMR1_CMPCFGA, TMR1_CMPCFGB, TMR2_CMPCFGA, and TMR2_CMPCFGB registers. Table 31 summarizes the output waveform generation modes. Table 31. Output waveform settings TMR_CMPMOD[3:0] Output waveform generation mode 0 Disable alteration 1 Toggle on count = TOP 2 Set on count = TOP, clear on count = CMPA 3 Set on count = TOP, clear on count = CMPB 4 Set to 1 5 Set on count = CMPA, clear on count = TOP 6 Toggle on count = CMPA 7 Set on count = CMPA, clear on count = CMPB 8 Clear to 0 9 Set on count = CMPB, clear on count = TOP 10 Set on count = CMPB, clear on count = CMPA 11 Toggle on count = CMPB 12 Toggle on count = ZERO 13 Set on count = ZERO, clear on count = TOP 14 Set on count = ZERO, clear on count = CMPA 15 Set on count = ZERO, clear on count = CMPB The output signals TMR1OA and TMR1OB from Timer 1, and TMR2OA and TMR2OB from Timer 2, are available on GPIO. For selecting alternate pin functions, refer to Table 17 and Table 18. Figure 14 and Figure 15 show examples of all timer output generation modes. 95/130 Functional description—application modules SN250 Figure 14. Timer output generation mode example—saw tooth, non-inverting Figure 15. Timer output generation mode example—alternating, non-inverting 96/130 SN250 7.4.4 Functional description—application modules Timer functionality (input capture) There are two capture registers that store the timer count value on a trigger condition from GPIO signals. The timer trigger signals TMR1IA and TMR1IB for Timer 1, and TMR2IA and TMR2IB for Timer 2 are provided by external signals routed to the GPIO pins. These timer trigger signals are synchronized to the main 12MHz clock, passed to an optional glitch filter, and followed by an edge detection circuitry. These functions are controlled by software with the register bits TMR_CAPMOD[1:0], and TMR_CAPFILT in the TMR1_CAPCFGA, TMR1_CAPCFGB, TMR2_CAPCFGA, and TMR2_CAPCFGB registers. Table 32. GPIO/Timer trigger conditioning TMR_CAPMOD[1:0] Detection Mode 0 Disabled 1 Rising Edge 2 Falling Edge 3 Either Edge All glitch filters consist of a flip-flop-driven, 4-bit shift register clocked with the main 12MHz clock. 7.4.5 Timer interrupt sources Each timer supports a number of interrupts sources: ● On overflow during up-count from all 1s to zero. ● On counter reaching output compare values stored in the TMR1_CMPA, TMR1_CMPB or TMR2_CMPA, and TMR2_CMPB registers. ● On counter reaching zero, TMR1_TOP, or TMR2_TOP. ● On capturing events from GPIO. To generate interrupts to the CPU, the interrupt masks in the INT_TMRCFG and INT_CFG registers must be enabled. 97/130 Functional description—application modules 7.4.6 SN250 Registers TMR1_CFG [0x450C] 15 0-R 14 0-R 13 0-R 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 0 0 TMR_EXTEN TMR_EN TMR_BIDIR TMR_DOWN TMR_1SHOT TMR_FILT TMR_EDGE 0-RW 3 0-RW 2 TMR_PSCL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 TMR_CLK 0-RW 1 0-RW 0 TMR_EXTEN [12] Control bit for the external enable mask on a pin. When this bit is clear, do not check status of the TMR1ENMSK pin. When this bit is set, check status of the TMR1ENMSK pin. TMR_EN [11] Set this bit to enable counting. To change other register bits, this bit must be cleared. TMR_BIDIR [10] Set this bit to enable bi-directional alternation mode. TMR_DOWN [9] Initial count direction after enabling the timer. Clear this bit to count up; set this bit to count down. TMR_1SHOT [8] Clear this bit for auto repetition mode. Set this bit for a single shot. TMR_PSCL [7:4] Clock divider setting (N). The possible clock divisors are: 0 − 2N (N = 0..10). TMR_FILT [3] Set this bit to enable clock source glitch filtering. TMR_EDGE [2] Clock source edge selection. Clear this bit for rising edge; set this bit for falling edge. TMR_CLK [1:0] Clock source selection: 0 = calibrated RC oscillator (default);1 = 32kHz; 2 = 12MHz; 3 = External (GPIO). TMR1_CNT [0x4500] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 TMR1_CNT TMR1_CNT 0-RW 7 TMR1_CNT 98/130 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 Current Timer 1 counter value. When read, returns the current timer counter. When written, overwrites the timer counter and restarts wrap detection. SN250 Functional description—application modules TMR1_TOP [0x4506] 15 1-RW 14 1-RW 13 1-RW 12 1-RW 11 1-RW 10 1-RW 9 1-RW 8 1-RW 1-RW 3 1-RW 2 1-RW 1 1-RW 0 TMR1_TOP TMR1_TOP 1-RW 7 TMR1_TOP 1-RW 6 [15:0] 1-RW 5 1-RW 4 Timer 1 threshold value. TMR1_CMPCFGA [0x450E] 15 0-RW 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R TMR_CMPEN 0 0 0 0 0 0 0 0 0 0 TMR_ CMPINV 0-R 7 0-R 6 0-R 5 0-RW 4 TMR_CMPMOD 0-RW 3 0-RW 2 TMR_CMPEN [15] Set this bit to enable output A. TMR_CMPINV [4] Set this bit to invert output A. TMR_CMPMOD [3:0] Output mode selection bits. Refer to Table 31 for the modes. 0-RW 1 0-RW 0 TMR1_CMPCFGB [0x4510] 15 0-RW 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R TMR_CMPEN 0 0 0 0 0 0 0 0 0 0 TMR_ CMPINV 0-R 7 0-R 6 0-R 5 0-RW 4 TMR_CMPMOD 0-RW 3 0-RW 2 TMR_CMPEN [15] Set this bit to enable output B. TMR_CMPINV [4] Set this bit to invert output B. TMR_CMPMOD [3:0] Output mode selection bits. Refer to Table 31 for the modes. 0-RW 1 0-RW 0 99/130 Functional description—application modules SN250 TMR1_CMPA [0x4508] 15 0-RW 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R TMR_CMPEN 0 0 0 0 0 0 0 0 0 0 TMR_ CMPINV 0-R 7 0-R 6 0-R 5 0-RW 4 TMR1_CMPA [15:0] TMR_CMPMOD 0-RW 3 0-RW 2 0-RW 1 0-RW 0 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 3 0-RW 2 0-RW 1 0-RW 0 Timer 1 compare A value. TMR1_CMPB [0x450A] 15 0-RW 14 0-RW 13 0-RW 12 0-RW TMR1_CMPB TMR1_CMPB 0-RW 7 TMR1_CMPB 0-RW 6 [15:0] 0-RW 5 0-RW 4 Timer 1 compare B value. TMR1_CAPCFGA [0x4512] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 TMR_ CAPFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 0 0-R 7 TMR_CAPMOD 0-RW 6 0-RW 5 TMR_CAPFILT [8] Set this bit to enable the input A filter. TMR_CAPMOD [6:5] Input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges. 100/130 SN250 Functional description—application modules TMR1_CAPCFGB [0x4514] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 TMR_ CAPFILT 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 0 0-R 7 TMR_CAPMOD 0-RW 6 0-RW 5 TMR_CAPFILT [8] Set this bit to enable the input B filter. TMR_CAPMOD [6:5] Input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges. TMR1_CAPA [0x4502] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 3 0-R 2 0-R 1 0-R 0 11 0-R 10 0-R 9 0-R 8 0-R 0-R 2 0-R 1 0-R 0 TMR1_CAPA TMR1_CAPA 0-R 7 TMR1_CAPA 0-R 6 [15:0] 0-R 5 0-R 4 Timer 1 capture A value. TMR1_CAPB [0x4504] 15 0-R 14 0-R 13 0-R 12 0-R TMR1_CAPB TMR1_CAPB 0-R 7 TMR1_CAPB 0-R 6 [15:0] 0-R 5 0-R 4 0-R 3 Timer 1 capture B value. 101/130 Functional description—application modules SN250 TMR2_CFG [0x458C] 15 0-R 14 0-R 13 0-R 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 0 0 TMR_EXTEN TMR_EN TMR_BIDIR TMR_DOWN TMR_1SHOT TMR_FILT TMR_EDGE 0-RW 3 0-RW 2 TMR_PSCL 0-RW 7 0-RW 6 0-RW 5 0-RW 4 TMR_CLK 0-RW 1 0-RW 0 TMR_EXTEN [12] Control bit for the external enable mask on a pin. When this bit is clear, do not check status of the TMR2ENMSK pin. When this bit is set, check status of the TMR2ENMSK pin. TMR_EN [11] Set this bit to enable counting. To change other register bits, this bit must be cleared. TMR_BIDIR [10] Set this bit to enable bi-directional alternation mode. TMR_DOWN [9] Initial count direction after enabling the timer. Clear this bit to count up; set this bit to count down. TMR_1SHOT [8] Clear this bit for auto repetition mode. Set this bit for a single shot. TMR_PSCL [7:4] Clock divider setting (N). The possible clock divisors are: 0 − 2N (N = 0..10). TMR_FILT [3] Set this bit to enable clock source glitch filtering. TMR_EDGE [2] Clock source edge selection. Clear this bit for rising edge; set this bit for falling edge. TMR_CLK [1:0] Clock source selection: 0 = calibrated RC oscillator (default); 1 = 32kHz; 2 = 12MHz; 3 = External (GPIO). TMR2_CNT [0x4580] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 2 0-RW 1 0-RW 0 TMR2_CNT TMR2_CNT 0-RW 7 TMR2_CNT 102/130 0-RW 6 [15:0] 0-RW 5 0-RW 4 0-RW 3 Current Timer 2 counter value. When read, returns the current timer counter. When written, overwrites the timer counter and restarts wrap detection. SN250 Functional description—application modules TMR2_TOP [0x4586] 15 1-RW 14 1-RW 13 1-RW 12 1-RW 11 1-RW 10 1-RW 9 1-RW 8 1-RW 1-RW 3 1-RW 2 1-RW 1 1-RW 0 TMR2_TOP TMR2_TOP 1-RW 7 TMR2_TOP 1-RW 6 [15:0] 1-RW 5 1-RW 4 Timer 2 threshold value. TMR2_CMPCFGA [0x458E] 15 0-RW 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R TMR_CMPEN 0 0 0 0 0 0 0 0 0 0 TMR_ CMPINV 0-R 7 0-R 6 0-R 5 0-RW 4 TMR_CMPMOD 0-RW 3 0-RW 2 TMR_CMPEN [15] Set this bit to enable output A. TMR_CMPINV [4] Set this bit to invert output A. TMR_CMPMOD [3:0] Output mode selection bits. Refer to Table 31 for the modes. 0-RW 1 0-RW 0 TMR2_CMPCFGB [0x4590] 15 0-RW 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R TMR_CMPEN 0 0 0 0 0 0 0 0 0 0 TMR_ CMPINV 0-R 7 0-R 6 0-R 5 0-RW 4 TMR_CMPMOD 0-RW 3 0-RW 2 TMR_CMPEN [15] Set this bit to enable output B. TMR_CMPINV [4] Set this bit to invert output B. TMR_CMPMOD [3:0] Output mode selection bits. Refer to Table 31 for the modes. 0-RW 1 0-RW 0 103/130 Functional description—application modules SN250 TMR2_CMPA [0x4588] 15 0-RW 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 3 0-RW 2 0-RW 1 0-RW 0 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0-RW 3 0-RW 2 0-RW 1 0-RW 0 TMR2_CMPA TMR2_CMPA 0-RW 7 TMR2_CMPA 0-RW 6 [15:0] 0-RW 5 0-RW 4 Timer 2 compare A value. TMR2_CMPB [0x458A] 15 0-RW 14 0-RW 13 0-RW 12 0-RW TMR2_CMPB TMR2_CMPB 0-RW 7 TMR2_CMPB 0-RW 6 [15:0] 0-RW 5 0-RW 4 Timer 2 compare B value. TMR2_CAPCFGA [0x4592] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 TMR_ CAPFILT 0 TMR_CAPMOD 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 0-R 7 0-RW 6 0-RW 5 TMR_CAPFILT [8] Set this bit to enable the input A filter. TMR_CAPMOD [6:5] Input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges. 104/130 SN250 Functional description—application modules TMR2_CAPCFGB [0x4594] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-RW 0 0 0 0 0 0 0 TMR_ CAPFILT 0 TMR_CAPMOD 0 0 0 0 0 0-R 4 0-R 3 0-R 2 0-R 1 0-R 0 0-R 7 0-RW 6 0-RW 5 TMR_CAPFILT [8] Set this bit to enable the input B filter. TMR_CAPMOD [6:5] Input edge triggering selection: 0 = disabled; 1 = rising; 2 = falling; 3 = both edges. TMR2_CAPA [0x4582] 15 0-R 14 0-R 13 0-R 12 0-R 11 0-R 10 0-R 9 0-R 8 0-R 0-R 2 0-R 1 0-R 0 TMR2_CAPA TMR2_CAPA 0-R 7 TMR2_CAPA 0-R 6 [15:0] 0-R 5 0-R 4 0-R 3 Timer 2 capture A value. TMR2_CAPB [0x4584] 15 14 13 12 11 10 9 8 0-R 0-R 0-R 0-R 0-R 0-R 0-R 0-R TMR2_CAPB TMR2_CAPB 0-R 0-R 0-R 0-R 0-R 0-R 0-R 0-R 7 6 5 4 3 2 1 0 TMR2_CAPB [15:0] Timer 2 capture B value. 105/130 Functional description—application modules SN250 INT_TMRCFG [0x462C] 15 0-R 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 INT_ TMR2CAPB INT_ TMR2CAPA INT_ TMR2CMPTOP INT_ TMR2CMPZ INT_ TMR2CMPB INT_ TMR2CMPA INT_ TMR2WRAP 0 INT_ TMR1CAPB INT_ TMR1CAPA INT_ TMR1CMPTOP INT_ TMR1CMPZ INT_ TMR1CMPB INT_ TMR1CMPA INT_ TMR1WRAP 0-R 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_TMR2CAPB [14] Timer 2 capture B interrupt enable. INT_TMR2CAPA [13] Timer 2 capture A interrupt enable. INT_TMR2CMPTOP [12] Timer 2 compare Top interrupt enable. INT_TMR2CMPZ [11] Timer 2 compare Zero interrupt enable. INT_TMR2CMPB [10] Timer 2 compare B interrupt enable. INT_TMR2CMPA [9] Timer 2 compare A interrupt enable. INT_TMR2WRAP [8] Timer 2 overflow interrupt enable. INT_TMR1CAPB [6] Timer 1 capture B interrupt enable. INT_TMR1CAPA [5] Timer 1 capture A interrupt enable. INT_TMR1CMPTOP [4] Timer 1 compare Top interrupt enable. INT_TMR1CMPZ [3] Timer 1 compare Zero interrupt enable. INT_TMR1CMPB [2] Timer 1 compare B interrupt enable. INT_TMR1CMPA [1] Timer 1 compare A interrupt enable. INT_TMR1WRAP [0] Timer 1 overflow interrupt enable. 106/130 SN250 Functional description—application modules INT_TMRFLAG [0x4614] 15 0-R 14 0-RW 13 0-RW 12 0-RW 11 0-RW 10 0-RW 9 0-RW 8 0-RW 0 INT_ TMR2CAPB INT_ TMR2CAPA INT_ TMR2CMPTOP INT_ TMR2CMPZ INT_ TMR2CMPB INT_ TMR2CMPA INT_ TMR2WRAP 0 INT_ TMR1CAPB INT_ TMR1CAPA INT_ TMR1CMPTOP INT_ TMR1CMPZ INT_ TMR1CMPB INT_ TMR1CMPA INT_ TMR1WRAP 0-R 7 0-RW 6 0-RW 5 0-RW 4 0-RW 3 0-RW 2 0-RW 1 0-RW 0 INT_TMR2CAPB [14] Timer 2 capture B interrupt pending. INT_TMR2CAPA [13] Timer 2 capture A interrupt pending. INT_TMR2CMPTOP [12] Timer 2 compare Top interrupt pending. INT_TMR2CMPZ [11] Timer 2 compare Zero interrupt pending. INT_TMR2CMPB [10] Timer 2 compare B interrupt pending. INT_TMR2CMPA [9] Timer 2 compare A interrupt pending. INT_TMR2WRAP [8] Timer 2 overflow interrupt pending. INT_TMR1CAPB [6] Timer 1 capture B interrupt pending. INT_TMR1CAPA [5] Timer 1 capture A interrupt pending. INT_TMR1CMPTOP [4] Timer 1 compare Top interrupt pending. INT_TMR1CMPZ [3] Timer 1 compare Zero interrupt pending. INT_TMR1CMPB [2] Timer 1 compare B interrupt pending. INT_TMR1CMPA [1] Timer 1 compare A interrupt pending. INT_TMR1WRAP [0] Timer 1 overflow interrupt pending. 107/130 Functional description—application modules 7.5 SN250 ADC module The ADC is a first-order sigma-delta converter sampling at 1MHz with programmable resolution and conversion rate. The conversion rate is programmed by setting the ADC_RATE bits in the ADC_CFG register. Table 33. ADC conversion rate ADC_RATE[2:0] Conversion Time Equivalent ADC Bits 0 32 μs 5, located in ADC_DATA[15:11] 1 64 μs 6, located in ADC_DATA[15:10] 2 128 μs 7, located in ADC_DATA[15:9] 3 256 μs 8, located in ADC_DATA[15:8] 4 512 μs 9, located in ADC_DATA[15:7] 5 1024 μs 10, located in ADC_DATA[15:6] 6 2048 μs 11, located in ADC_DATA[15:5] 7 4096 μs 12, located in ADC_DATA[15:4] The analog input of the ADC can be chosen from various sources and is configured with the ADC_SEL bits in the ADC_CFG register. As described in Table 34, the ADC inputs can be single-ended (routed individually to ADC0, ADC1, ADC2, or ADC3) or differential (routed to pairs ADC0-ADC1 and ADC2-ADC3). For selecting alternate pin functions, refer to Table 17 and Table 18. Table 34. ADC inputs ADC_SEL[3:0] Analog Source of ADC GPIO Pin Purpose 0 ADC0 4 Single-ended 1 ADC1 5 Single-ended 2 ADC2 6 Single-ended 3 ADC3 7 Single-ended 4 (1/4) * VDD_PADS (2.1–3.6V pad supply) Supply monitoring 5 (1/2) * VDD (1.8V core supply) Supply monitoring 6 RESERVED 7 VSS (0V) 8 VREF 8 Calibration 9 ADC0–ADC1 4–5 Differential 10 ADC2–ADC3 6–7 Differential Calibration Setting the ADC_EN bit in the ADC_CFG register will cause the ADC to immediately begin conversions. The ADC will continually generate conversions until the ADC_EN bit is cleared. When each conversion completes, an INT_ADC interrupt is generated. In order for this to interrupt the CPU the interrupt mask INT_ADC must be enabled in the INT_CFG register. The INT_ADC interrupt is the only means for determining when a conversion completes. After each INT_ADC interrupt, the INT_ADC interrupt bit must be cleared to detect completion of the next conversion. 108/130 SN250 Functional description—application modules To ensure the pipelined digital filter in the ADC is flushed, ADC_EN should be cleared before changes are made to ADC_SEL or ADC_RATE. Discard the first sample after ADC_EN is set. The ADC uses an internal reference, VREF, which may be routed out to the alternate pin function of GPIO8, VREF_OUT. VREF_OUT is only enabled when the ADC_EN bit in the ADC_CFG register is set. VREF is trimmed as close to 1.2V as possible by the ZNet software, using the regulated supply (VDD) as reference. VREF is able to source modest current (see Table 36) and is stable under capacitive loads. The ADC cannot accept an external VREF input. For selecting alternate pin functions, refer to Table 17 and Table 18. While the ADC Module supports both single-ended and differential inputs, the ADC input stage is differential. Single-ended operation is provided by internally connecting one of the differential inputs to VREF/2 while fully differential operation uses two external signals. The full-scale differential input range spans -VREF to +VREF and the single-ended input range spans 0 to VREF. Fully differential operation is recommended only when large common-mode signals are present. To correct differential input for offset and gain, each side of the input should be sampled individually using single-ended operation, so that they may be calibrated against VREF. Sampling of internal connections VSS and VREF allow for offset and gain calibration of the ADC in applications where absolute accuracy is important. Measurement of the unregulated supply VDD_PADS, 2.1-3.6V pad supply, allows battery voltage to be monitored. Measurement of the regulated supply VDD, 1.8V core supply, provides an accurate means of calibrating the ADC as the regulator is factory trimmed. Offset and gain correction using VREF or VDD reduces both ADC gain errors and reference errors but it is limited by the absolute accuracy of the supply. Correction using VREF is recommended because VREF is calibrated by the ZNet software against VDD, which is factory trimmed. Table 35 shows the equations used. Table 35. Offset and gain correction calculation Calculation Type Corrected Sample Absolute Voltage Offset corrected N = ( N X – N VSS ) Offset and gain corrected using VREF, normalized to VREF ( N X – N VSS ) « 16 N = --------------------------------------------( N VREF – N VSS ) N × VREF ) V = (------------------------------16 2 Offset and gain corrected using VDD, normalized to VDD ( N X – N VSS ) « 16 N = ------------------------------------------------2 × ( N VDD – N VSS ) ( N × VDD ) V = ---------------------------16 2 109/130 Functional description—application modules SN250 Equation notes: ● All N are 16-bit numbers. ● NX is a sampling of the desired analog source. ● NVSS is a sampling of ground. Due to the nature of the ADC’s internal design, ground does not yield 0x0000 in the ADC_DATA register. Instead, ground yields a value closer to 1/3 of the range — for example, 0x5200. ● NVREF is a sampling of VREF. Due to the nature of the ADC’s internal design, VREF does not yield 0xFFFF in the ADC_DATA register. Instead, VREF yields a value closer to 2/3 of the range — for example, 0xA800. ● NVDD is a sampling of the regulated supply, VDD/2. ●