M24M02-DRMN6TP

M24M02-DR M24M02-R 2-Mbit serial I²C bus EEPROM Datasheet - production data Features SO8 (MN) 150 mil width WLCSP • Compatible with all I2C bus modes: – 1 MHz – 400 kHz – 100 kHz • Memory array: – 2 Mbit (256 Kbyte) of EEPROM – Page size: 256 byte – Additional Write lockable page (M24M02DR order codes) • Single supply voltage: – 1.8 V to 5.5 V over –40 °C / +85 °C • Write: – Byte Write within 10 ms – Page Write within 10 ms • Random and sequential Read modes Unsawn wafer • Write protect of the whole memory array • Enhanced ESD/Latch-Up protection • More than 4 million Write cycles • More than 200-years data retention Packages • SO8 ECOPACK2® • WLCSP ECOPACK2® • Unsawn wafer (each die is tested) • RoHS compliant and halogen-free (ECOPACK2®) January 2018 This is information on a product in full production. DocID18204 Rev 10 1/40 www.st.com Contents M24M02-DR M24M02-R Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 Signal description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 Serial Clock (SCL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 Serial Data (SDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3 Chip Enable (E2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 Write Control (WC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.5 VSS (ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.6 Supply voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6.1 Operating supply voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6.2 Power-up conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6.3 Device reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6.4 Power-down conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3 Memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4 Device operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5 4.1 Start condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2 Stop condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.3 Data input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.4 Acknowledge bit (ACK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.5 Device addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1 5.2 Write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1.1 Byte Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1.2 Page Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1.3 Write Identification Page (M24M02-DR only) . . . . . . . . . . . . . . . . . . . . . 17 5.1.4 Lock Identification Page (M24M02-DR only) . . . . . . . . . . . . . . . . . . . . . 17 5.1.5 ECC (Error Correction Code) and Write cycling . . . . . . . . . . . . . . . . . . 17 5.1.6 Minimizing Write delays by polling on ACK . . . . . . . . . . . . . . . . . . . . . . 18 Read operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.2.1 2/40 Random Address Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 DocID18204 Rev 10 M24M02-DR M24M02-R Contents 5.2.2 Current Address Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.2.3 Sequential Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.2.4 Read Identification Page (M24M02-DR only) . . . . . . . . . . . . . . . . . . . . 20 5.2.5 Read the lock status (M24M02-DR only) . . . . . . . . . . . . . . . . . . . . . . . . 21 6 Initial delivery state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7 Maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8 DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 9 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.1 SO8N package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.2 WLCSP package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 10 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 11 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 DocID18204 Rev 10 3/40 3 List of tables M24M02-DR M24M02-R List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Table 14. Table 15. Table 16. Table 17. Table 18. Table 19. 4/40 Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Signals vs. bump position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Device select code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Most significant address byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Least significant address byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 AC measurement conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Input parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Cycling performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Memory cell data retention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 DC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 400 kHz AC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1 MHz AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 SO8N – 3.9x4.9 mm, 8-lead plastic small outline, 150 mils body width, package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 WLCSP- 8-bump, 3.556 x 2.011 mm, wafer level chip scale package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Ordering information scheme (unsawn wafer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 DocID18204 Rev 10 M24M02-DR M24M02-R List of figures List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SO8 connections, top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 WLCSP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Chip enable inputs connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Write mode sequences with WC = 0 (data write enabled) . . . . . . . . . . . . . . . . . . . . . . . . . 15 Write mode sequences with WC = 1 (data write inhibited) . . . . . . . . . . . . . . . . . . . . . . . . . 16 Write cycle polling flowchart using ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Read mode sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 AC measurement I/O waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 13. Maximum Rbus value versus bus parasitic capacitance Cbus) for an I2C bus at maximum frequency fC = 1MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 SO8N – 3.9x4.9 mm, 8-lead plastic small outline, 150 mils body width, package outline . 32 SO8N – 3.9x4.9 mm, 8-lead plastic small outline, 150 mils body width, package recommended footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 WLCSP- 8-bump, 3.556 x 2.011 mm, wafer level chip scale package outline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 WLCSP- 8-bump, 3.556 x 2.011 mm, wafer level chip scale package recommended footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Maximum Rbus value versus bus parasitic capacitance (Cbus) for an I2C bus at maximum frequency fC = 400 kHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 DocID18204 Rev 10 5/40 5 Description 1 M24M02-DR M24M02-R Description The M24M02 is a 2 Mbit I2C-compatible EEPROM (Electrically Erasable PROgrammable Memory) organized as 256 K × 8 bits. The M24M02-DR and M24M02-R can operate with a supply voltage from 1.8 V to 5.5 V, over an ambient temperature range of –40 °C / +85 °C. The M24M02-DR offers an additional page, named the Identification Page (256 byte). The Identification Page can be used to store sensitive application parameters which can be (later) permanently locked in Read-only mode. Figure 1. Logic diagram 9&& ( 6'$ 00[5 6&/ :& 966 069 Table 1. Signal names Signal name Function Direction E2 Chip Enable Input SDA Serial Data I/O SCL Serial Clock Input WC Write Control Input VCC Supply voltage - VSS Ground - Figure 2. SO8 connections, top view $5   6 ## $5   7# %   3#, 6 33   3$! !)V 1. DU: Don’t use (no signal should be applied on this pin; if connected, must be connected to VSS) 2. See Section 9: Package information for package dimensions, and how to identify pin 1 6/40 DocID18204 Rev 10 M24M02-DR M24M02-R Description Figure 3. WLCSP connections         $ $ % % & & ' ' 0DUNLQJVLGH WRSYLHZ %XPSVLGH ERWWRPYLHZ 069 1. DU: Don’t use (no signal should be applied on this pin; if connected, must be connected to Vss) 2. See Section 9: Package information for package dimensions, and how to identify pin 1. Table 2. Signals vs. bump position Position A B C D 1 - - SCL - 2 VCC WC - SDA 3 DU - - VSS 4 - DU E2 - DocID18204 Rev 10 7/40 39 Signal description M24M02-DR M24M02-R 2 Signal description 2.1 Serial Clock (SCL) The signal applied on the SCL input is used to strobe the data available on SDA(in) and to output the data on SDA(out). 2.2 Serial Data (SDA) SDA is an input/output used to transfer data in or data out of the device. SDA(out) is an open drain output that may be wire-OR’ed with other open drain or open collector signals on the bus. A pull-up resistor must be connected (Figure 12 indicates how to calculate the value of the pull-up resistor). 2.3 Chip Enable (E2) This input signal is used to set the value that is to be looked for on the bit b3 of the 7-bit device select code. This input must be tied to VCC or VSS, to establish the device select code as shown in Figure 4. When not connected (left floating), this input is read as low (0 Figure 4. Chip enable inputs connection 9&& 9&& 0[[[ 0[[[ (L (L 966 2.4 966 $L Write Control (WC) This input signal is useful for protecting the entire contents of the memory from inadvertent write operations. Write operations are disabled to the entire memory array when Write Control (WC) is driven high. Write operations are enabled when Write Control (WC) is either driven low or left floating. When Write Control (WC) is driven high, device select and address bytes are acknowledged, Data bytes are not acknowledged. 2.5 VSS (ground) VSS is the reference for the VCC supply voltage. 8/40 DocID18204 Rev 10 M24M02-DR M24M02-R Signal description 2.6 Supply voltage (VCC) 2.6.1 Operating supply voltage (VCC) Prior to selecting the memory and issuing instructions to it, a valid and stable VCC voltage within the specified [VCC(min), VCC(max)] range must be applied (see Operating conditions in Section 8: DC and AC parameters). In order to secure a stable DC supply voltage, it is recommended to decouple the VCC line with a suitable capacitor (usually of the order of 10 nF to 100 nF) close to the VCC/VSS package pins. This voltage must remain stable and valid until the end of the transmission of the instruction and, for a write instruction, until the completion of the internal write cycle (tW). 2.6.2 Power-up conditions The VCC voltage has to rise continuously from 0 V up to the minimum VCC operating voltage (see Operating conditions in Section 8: DC and AC parameters). 2.6.3 Device reset In order to prevent inadvertent write operations during power-up, a power-on-reset (POR) circuit is included. At power-up, the device does not respond to any instruction until VCC has reached the internal reset threshold voltage. This threshold is lower than the minimum VCC operating voltage (see Operating conditions in Section 8: DC and AC parameters). When VCC passes over the POR threshold, the device is reset and enters the Standby Power mode; however, the device must not be accessed until VCC reaches a valid and stable DC voltage within the specified [VCC(min), VCC(max)] range (see Operating conditions in Section 8: DC and AC parameters). In a similar way, during power-down (continuous decrease in VCC), the device must not be accessed when VCC drops below VCC(min). When VCC drops below the power-on-reset threshold voltage, the device stops responding to any instruction sent to it. 2.6.4 Power-down conditions During power-down (continuous decrease in VCC), the device must be in the Standby Power mode (mode reached after decoding a Stop condition, assuming that there is no internal write cycle in progress). DocID18204 Rev 10 9/40 39 Memory organization 3 M24M02-DR M24M02-R Memory organization The memory is organized as shown below. Figure 5. Block diagram 7# % (IGHVOLTAGE GENERATOR #ONTROLLOGIC 3#, 3$! )/SHIFTREGISTER $ATA REGISTER 9DECODER !DDRESSREGISTER ANDCOUNTER PAGE )DENTIFICATIONPAGE 8DECODER -36 10/40 DocID18204 Rev 10 M24M02-DR M24M02-R 4 Device operation Device operation The device supports the I2C protocol. This is summarized in Figure 6. Any device that sends data on to the bus is defined to be a transmitter, and any device that reads the data to be a receiver. The device that controls the data transfer is known as the bus master, and the other as the slave device. A data transfer can only be initiated by the bus master, which will also provide the serial clock for synchronization. The device is always a slave in all communications. Figure 6. I2C bus protocol DocID18204 Rev 10 11/40 39 Device operation 4.1 M24M02-DR M24M02-R Start condition Start is identified by a falling edge of Serial Data (SDA) while Serial Clock (SCL) is stable in the high state. A Start condition must precede any data transfer instruction. The device continuously monitors (except during a Write cycle) Serial Data (SDA) and Serial Clock (SCL) for a Start condition. 4.2 Stop condition Stop is identified by a rising edge of Serial Data (SDA) while Serial Clock (SCL) is stable and driven high. A Stop condition terminates communication between the device and the bus master. A Read instruction that is followed by NoAck can be followed by a Stop condition to force the device into the Standby mode. A Stop condition at the end of a Write instruction triggers the internal Write cycle. 4.3 Data input During data input, the device samples Serial Data (SDA) on the rising edge of Serial Clock (SCL). For correct device operation, Serial Data (SDA) must be stable during the rising edge of Serial Clock (SCL), and the Serial Data (SDA) signal must change only when Serial Clock (SCL) is driven low. 4.4 Acknowledge bit (ACK) The acknowledge bit is used to indicate a successful byte transfer. The bus transmitter, whether it be bus master or slave device, releases Serial Data (SDA) after sending eight bits of data. During the 9th clock pulse period, the receiver pulls Serial Data (SDA) low to acknowledge the receipt of the eight data bits. 12/40 DocID18204 Rev 10 M24M02-DR M24M02-R 4.5 Device operation Device addressing To start communication between the bus master and the slave device, the bus master must initiate a Start condition. Following this, the bus master sends the device select code, shown in Table 3 (most significant bit first). Table 3. Device select code Chip Enable Device type identifier(1) MSB address bits RW b7 b6 b5 b4 b3 b2 b1 b0 Device select code when addressing the memory array 1 0 1 0 E2(2) A17 A16 RW Device select code when addressing the Identification page 1 0 1 1 E2(2) X X RW 1. The most significant bit, b7, is sent first. 2. E2 bit value is compared to the logic level applied on the input pin E2. When the device select code is received, the device only responds if the Chip Enable Address is the same as the value on the Chip Enable (E2) input. The 8th bit is the Read/Write bit (RW). This bit is set to 1 for Read and 0 for Write operations. If a match occurs on the device select code, the corresponding device gives an acknowledgment on Serial Data (SDA) during the 9th bit time. If the device does not match the device select code, it deselects itself from the bus, and goes into Standby mode. DocID18204 Rev 10 13/40 39 Instructions M24M02-DR M24M02-R 5 Instructions 5.1 Write operations Following a Start condition the bus master sends a device select code with the R/W bit (RW) reset to 0. The device acknowledges this, as shown in Figure 7, and waits for two address bytes. The device responds to each address byte with an acknowledge bit, and then waits for the data byte. Table 4. Most significant address byte A15 A14 A13 A12 A11 A10 A9 A8 A1 A0 Table 5. Least significant address byte A7 A6 A5 A4 A3 A2 The 256 Kbytes (2 Mb) are addressed with 18 address bits, the 16 lower address bits being defined by the two address bytes and the most significant address bits (A17, A16) being included in the Device Select code (see Table 4). When the bus master generates a Stop condition immediately after a data byte Ack bit (in the “10th bit” time slot), either at the end of a Byte Write or a Page Write, the internal Write cycle tW is triggered. A Stop condition at any other time slot does not trigger the internal Write cycle. After the Stop condition and the successful completion of an internal Write cycle (tW), the device internal address counter is automatically incremented to point to the next byte after the last modified byte. During the internal Write cycle, Serial Data (SDA) is disabled internally, and the device does not respond to any requests. If the Write Control input (WC) is driven High, the Write instruction is not executed and the accompanying data bytes are not acknowledged, as shown in Figure 8. 14/40 DocID18204 Rev 10 M24M02-DR M24M02-R 5.1.1 Instructions Byte Write After the device select code and the address byte, the bus master sends one data byte. If the addressed location is Write-protected, by Write Control (WC) being driven high, the device replies with NoAck, and the location is not modified. If, instead, the addressed location is not Write-protected, the device replies with Ack. The bus master terminates the transfer by generating a Stop condition, as shown in Figure 7. Figure 7. Write mode sequences with WC = 0 (data write enabled) DocID18204 Rev 10 15/40 39 Instructions 5.1.2 M24M02-DR M24M02-R Page Write The Page Write mode allows up to 256 byte to be written in a single Write cycle, provided that they are all located in the same page in the memory: that is, the most significant memory address bits, A17/A8, are the same. If more bytes are sent than will fit up to the end of the page, a “roll-over” occurs, i.e. the bytes exceeding the page end are written on the same page, from location 0. The bus master sends from 1 to 256 byte of data, each of which is acknowledged by the device if Write Control (WC) is low. If Write Control (WC) is high, the contents of the addressed memory location are not modified, and each data byte is followed by a NoAck, as shown in Figure 8. After each transferred byte, the internal page address counter is incremented. The transfer is terminated by the bus master generating a Stop condition. Figure 8. Write mode sequences with WC = 1 (data write inhibited) 16/40 DocID18204 Rev 10 M24M02-DR M24M02-R 5.1.3 Instructions Write Identification Page (M24M02-DR only) The Identification Page (256 byte) is an additional page which can be written and (later) permanently locked in Read-only mode. It is written by issuing the Write Identification Page instruction. This instruction uses the same protocol and format as Page Write (into memory array), except for the following differences: • Device type identifier = 1011b • MSB address bits A17/A8 are don't care except for address bit A10 which must be ‘0’. LSB address bits A7/A0 define the byte address inside the Identification page. If the Identification page is locked, the data bytes transferred during the Write Identification Page instruction are not acknowledged (NoAck). 5.1.4 Lock Identification Page (M24M02-DR only) The Lock Identification Page instruction (Lock ID) permanently locks the Identification page in Read-only mode. The Lock ID instruction is similar to Byte Write (into memory array) with the following specific conditions: 5.1.5 • Device type identifier = 1011b • Address bit A10 must be ‘1’; all other address bits are don't care • The data byte must be equal to the binary value xxxx xx1x, where x is don't care ECC (Error Correction Code) and Write cycling The Error Correction Code (ECC) is an internal logic function which is transparent for the I2C communication protocol. The ECC logic is implemented on each group of four EEPROM bytes(a). Inside a group, if a single bit out of the four bytes happens to be erroneous during a Read operation, the ECC detects this bit and replaces it with the correct value. The read reliability is therefore much improved. Even if the ECC function is performed on groups of four bytes, a single byte can be written/cycled independently. In this case, the ECC function also writes/cycles the three other bytes located in the same group(a). As a consequence, the maximum cycling budget is defined at group level and the cycling can be distributed over the 4 bytes of the group: the sum of the cycles seen by byte0, byte1, byte2 and byte3 of the same group must remain below the maximum value defined Table 10: Cycling performance. a.A group of four bytes is located at addresses [4*N, 4*N+1, 4*N+2, 4*N+3], where N is an integer. DocID18204 Rev 10 17/40 39 Instructions 5.1.6 M24M02-DR M24M02-R Minimizing Write delays by polling on ACK During the internal Write cycle, the device disconnects itself from the bus, and writes a copy of the data from its internal latches to the memory cells. The maximum Write time (tw) is shown in AC characteristics tables in Section 8: DC and AC parameters, but the typical time is shorter. To make use of this, a polling sequence can be used by the bus master. The sequence, as shown in Figure 9, is: • Initial condition: a Write cycle is in progress. • Step 1: the bus master issues a Start condition followed by a device select code (the first byte of the new instruction). • Step 2: if the device is busy with the internal Write cycle, no Ack will be returned and the bus master goes back to Step 1. If the device has terminated the internal Write cycle, it responds with an Ack, indicating that the device is ready to receive the second part of the instruction (the first byte of this instruction having been sent during Step 1). Figure 9. Write cycle polling flowchart using ACK :ULWHF\FOH LQSURJUHVV 6WDUWFRQGLWLRQ 'HYLFHVHOHFW ZLWK5:  12 $&. UHWXUQHG