CY28441ZXCT

CY28441 Clock Generator for Intel Alviso Chipset Features • 33-MHz PCI clock • Low-voltage frequency select input • Compliant to Intel CK410M • I2C support with readback capabilities • Supports Intel Pentium®-M CPU • Ideal Lexmark Spread Spectrum profile for maximum electromagnetic interference (EMI) reduction • Selectable CPU frequencies • Differential CPU clock pairs • 3.3V power supply • 100-MHz differential SRC clocks • 56-pin TSSOP package • 96-MHz differential dot clock • 48-MHz USB clocks • SRC clocks independently stoppable through CLKREQ#[A:B] CPU SRC PCI REF DOT96 USB_48 x2 / x3 x6 / x7 x6 x1 x1 x1 Block Diagram XIN XOUT CPU_STP# PCI_STP# CLKREQ[A:B]# XTAL OSC PLL1 Pin Configuration VDD_REF REF PLL Ref Freq Divider Network FS_[C:A] VTT_PWRGD# IREF PD PLL2 SDATA SCLK I2C Logic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 CY28441 VDD_PCI VSS_PCI PCI3 VDD_CPU PCI4 CPUT[0:1], CPUC[0:1], CPU(T/C)2_ITP] PCI5 VDD_SRC VSS_PCI SRCT[0:5], SRCC[0:5] VDD_PCI PCIF0/ITP_EN PCIF1 VTT_PWRGD#/PD VDD_PCI VDD_48 PCI[2:5] USB_48/FS_A VDD_PCIF VSS_48 PCIF[0:1] DOT96T DOT96C VDD_48 MHz FS_B/TEST_MODE DOT96T SRCT0 DOT96C SRCC0 USB_48 SRCT1 SRCC1 VDD_SRC SRCT2 SRCC2 SRCT3 SRCC3 SRC4_SATAT SRC4_SATAC VDD_SRC 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 PCI2 PCI_STP# CPU_STP# FS_C/TEST_SEL REF VSS_REF XIN XOUT VDD_REF SDATA SCLK VSS_CPU CPUT0 CPUC0 VDD_CPU CPUT1 CPUC1 IREF VSSA VDDA CPUT2_ITP/SRCT7 CPUC2_ITP/SRCC7 VDD_SRC CLKREQA# CLKREQB# SRCT5 SRCC5 VSS_SRC 56 TSSOP Cypress Semiconductor Corporation Document #: 38-07679 Rev. ** • 3901 North First Street • San Jose, CA 95134 • 408-943-2600 Revised July 13, 2004 [+] Feedback CY28441 Pin Description Pin No. Name Type Description 33, 32 CLKREQA#, CLKREQB#, I, PU 3.3V LVTTL input for enabling assigned SRC clock, active LOW. CLKREQA# defaults to enable/disable SRCT/C4, CLKREQB# defaults to enable/disable SRCT/C5. Assignment can be changed via SMBUS register Byte 8. 54 CPU_STP# I, PU 3.3V LVTTL input for CPU_STP# active LOW. 44, 43, 41, 40 CPUT/C O, DIF Differential CPU clock outputs. 36, 35 CPUT2_ITP/SRCT7, CPUC2_ITP/SRCC7 O, DIF Selectable differential CPU or SRC clock output. ITP_EN = 0 @ VTT_PWRGD# assertion = SRC7 ITP_EN = 1 @ VTT_PWRGD# assertion = CPU2 14, 15 DOT96T, DOT96C O, DIF Fixed 96-MHz clock output. 12 FS_A/USB_48 I/O, SE 3.3V-tolerant input for CPU frequency selection/fixed 48-MHz clock output. Refer to DC Electrical Specifications table for VIL_FS,VIH_FS specifications. 16 FS_B/TEST_MODE I 3.3V-tolerant input for CPU frequency selection. Selects Ref/N or Hi-Z when in test mode 0 = Hi-Z, 1 = Ref/N Refer to DC Electrical Specifications table for VIL_FS,VIH_FS specifications. 53 FS_C/TEST_SEL I 3.3V-tolerant input for CPU frequency selection. Selects test mode if pulled to greater than 2.0V when VTT_PWRGD# is asserted low. Refer to DC Electrical Specifications table for VIL_FS,VIH_FS specifications. 39 IREF I A precision resistor is attached to this pin, which is connected to the internal current reference. 56, 3, 4, 5 PCI O, SE 33-MHz clocks. 55 PCI_STP# I, PU 8 PCIF0/ITP_EN I/O, SE 33-MHz clock/CPU2 select (sampled on the VTT_PWRGD# assertion). 1 = CPU2_ITP, 0 = SRC7 9 PCIF1 O, SE 33-MHz clock. 52 REF O, SE Reference clock. 3.3V 14.318-MHz clock output. 46 SCLK I 47 SDATA I/O 26, 27 SRC4_SATAT, SRC4_SATAC 24, 25, 22, SRCT/C 23, 19, 20, 17, 18, 31, 30 11 3.3V LVTTL input for PCI_STP# active LOW. SMBus-compatible SCLOCK. SMBus-compatible SDATA. O, DIF Differential serial reference clock. Recommended output for SATA. O, DIF Differential serial reference clocks. VDD_48 PWR 3.3V power supply for outputs. 42 VDD_CPU PWR 3.3V power supply for outputs. 1,7 VDD_PCI PWR 3.3V power supply for outputs. 48 VDD_REF PWR 3.3V power supply for outputs. 21, 28, 34 VDD_SRC PWR 3.3V power supply for outputs. 37 VDDA PWR 3.3V power supply for PLL. 13 VSS_48 GND Ground for outputs. 45 VSS_CPU GND Ground for outputs. 2,6 VSS_PCI GND Ground for outputs. 51 VSS_REF GND Ground for outputs. 29 VSS_SRC GND Ground for outputs. 38 VSSA GND Ground for PLL. 10 VTT_PWRGD#/PD Document #: 38-07679 Rev. ** I 3.3V LVTTL input is a level sensitive strobe used to latch the USB_48/FS_A, FS_B, FS_C/TEST_SEL and PCIF0/ITP_EN inputs. After VTT_PWRGD# (active LOW) assertion, this pin becomes a real-time input for asserting power-down (active HIGH). Page 2 of 20 [+] Feedback CY28441 Pin Description Pin No. Name 50 XIN 49 XOUT Type I Description 14.318-MHz crystal input. O, SE 14.318-MHz crystal output. Frequency Select Pins (FS_A, FS_B and FS_C) Host clock frequency selection is achieved by applying the appropriate logic levels to FS_A, FS_B, FS_C inputs prior to VTT_PWRGD# assertion (as seen by the clock synthesizer). Upon VTT_PWRGD# being sampled LOW by the clock chip (indicating processor VTT voltage is stable), the clock chip samples the FS_A, FS_B and FS_C input values. For all logic levels of FS_A, FS_B and FS_C, VTT_PWRGD# employs a one-shot functionality in that once a valid low on VTT_PWRGD# has been sampled, all further VTT_PWRGD#, FS_A, FS_B and FS_C transitions will be ignored, except in test mode. See Table 1. Serial Data Interface To enhance the flexibility and function of the clock synthesizer, a two-signal serial interface is provided. Through the Serial Data Interface, various device functions, such as individual clock output buffers, can be individually enabled or disabled. The registers associated with the Serial Data Interface initialize to their default setting upon power-up, and therefore use of this interface is optional. Clock device register changes are normally made upon system initialization, if any are required. The interface cannot be used during system operation for power management functions. Data Protocol The clock driver serial protocol accepts Byte Write, Byte Read, Block Write, and Block Read operations from the controller. For Block Write/Read operation, the bytes must be accessed in sequential order from lowest to highest byte (most significant bit first) with the ability to stop after any complete byte has been transferred. For Byte Write and Byte Read operations, the system controller can access individually indexed bytes. The offset of the indexed byte is encoded in the command code, as described in Table 2. The Block Write and Block Read protocol is outlined in Table 3 while Table 4 outlines the corresponding Byte Write and Byte Read protocol. The slave receiver address is 11010010 (D2h). Table 1. Frequency Select Table FS_A, FS_B and FS_C FS_C FS_B FS_A CPU SRC PCIF/PCI REF0 DOT96 USB 1 0 1 100 MHz 100 MHz 33 MHz 14.318 MHz 96 MHz 48 MHz 0 0 1 133 MHz 100 MHz 33 MHz 14.318 MHz 96 MHz 48 MHz 0 1 1 0 1 0 0 0 0 1 0 0 1 1 0 1 1 1 RESERVED Table 2. Command Code Definition Bit 7 (6:0) Description 0 = Block Read or Block Write operation, 1 = Byte Read or Byte Write operation Byte offset for Byte Read or Byte Write operation. For Block Read or Block Write operations, these bits should be '0000000' Table 3. Block Read and Block Write Protocol Block Write Protocol Bit 1 8:2 Description Start Slave address – 7 bits Block Read Protocol Bit 1 8:2 Description Start Slave address – 7 bits 9 Write 9 Write 10 Acknowledge from slave 10 Acknowledge from slave 18:11 Command Code – 8 bits 18:11 Command Code – 8 bits 19 Acknowledge from slave 19 Acknowledge from slave Document #: 38-07679 Rev. ** Page 3 of 20 [+] Feedback CY28441 Table 3. Block Read and Block Write Protocol (continued) Block Write Protocol Bit 27:20 28 36:29 37 45:38 Block Read Protocol Description Bit Byte Count – 8 bits 20 Acknowledge from slave 27:21 Data byte 1 – 8 bits Acknowledge from slave Data byte 2 – 8 bits Acknowledge from slave .... Data Byte /Slave Acknowledges .... Data Byte N –8 bits .... Acknowledge from slave .... Stop Slave address – 7 bits 28 Read = 1 29 Acknowledge from slave 37:30 46 Description Repeat start 38 46:39 47 55:48 Byte Count from slave – 8 bits Acknowledge Data byte 1 from slave – 8 bits Acknowledge Data byte 2 from slave – 8 bits 56 Acknowledge .... Data bytes from slave / Acknowledge .... Data Byte N from slave – 8 bits .... NOT Acknowledge .... Stop Table 4. Byte Read and Byte Write Protocol Byte Write Protocol Bit 1 8:2 Byte Read Protocol Description Bit Start 1 Slave address – 7 bits 8:2 Description Start Slave address – 7 bits 9 Write 9 Write 10 Acknowledge from slave 10 Acknowledge from slave 18:11 Command Code – 8 bits 18:11 Command Code – 8 bits 19 Acknowledge from slave 19 Acknowledge from slave 27:20 Data byte – 8 bits 20 28 Acknowledge from slave 29 Stop 27:21 Repeated start Slave address – 7 bits 28 Read 29 Acknowledge from slave 37:30 Data from slave – 8 bits 38 NOT Acknowledge 39 Stop Control Registers Byte 0:Control Register 0 Bit @Pup Name 7 1 CPUT2_ITP/SRCT7 CPUC2_ITP/SRCC7 6 1 RESERVED 5 1 SRC[T/C]5 SRC[T/C]5 Output Enable 0 = Disable (Hi-Z), 1 = Enable 4 1 SRC[T/C]4 SRC[T/C]4 Output Enable 0 = Disable (Hi-Z), 1 = Enable 3 1 SRC[T/C]3 SRC[T/C]3 Output Enable 0 = Disable (Hi-Z), 1 = Enable Document #: 38-07679 Rev. ** Description CPU[T/C]2_ITP/SRC[T/C]7 Output Enable 0 = Disable (Hi-Z), 1 = Enable RESERVED Page 4 of 20 [+] Feedback CY28441 Byte 0:Control Register 0 (continued) Bit @Pup Name Description 2 1 SRC[T/C]2 SRC[T/C]2 Output Enable 0 = Disable (Hi-Z), 1 = Enable 1 1 SRC[T/C]1 SRC[T/C]1 Output Enable 0 = Disable (Hi-Z), 1 = Enable 0 1 SRC[T/C]0 SRC[T/C]0 Output Enable 0 = Disable (Hi-Z), 1 = Enable Byte 1: Control Register 1 Bit @Pup Name 7 1 PCIF0 Description 6 1 DOT_96T/C 5 1 USB_48 4 1 REF 3 0 Reserved Reserved 2 1 CPU[T/C]1 CPU[T/C]1 Output Enable 0 = Disable (Hi-Z), 1 = Enabled 1 1 CPU[T/C]0 CPU[T/C]0 Output Enable 0 = Disable (Hi-Z), 1 = Enabled 0 0 CPUT/C SRCT/C PCIF PCI PCIF0 Output Enable 0 = Disabled, 1 = Enabled DOT_96 MHz Output Enable 0 = Disable (Hi-Z), 1 = Enabled USB_48 MHz Output Enable 0 = Disabled, 1 = Enabled REF Output Enable 0 = Disabled, 1 = Enabled Spread Spectrum Enable 0 = Spread off, 1 = Spread on Byte 2: Control Register 2 Bit @Pup Name Description 7 1 PCI5 PCI5 Output Enable 0 = Disabled, 1 = Enabled 6 1 PCI4 PCI4 Output Enable 0 = Disabled, 1 = Enabled 5 1 PCI3 PCI3 Output Enable 0 = Disabled, 1 = Enabled 4 1 PCI2 PCI2 Output Enable 0 = Disabled, 1 = Enabled 3 1 PCI PCI Output Drive strength 0 = Low drive 1 = High drive 2 1 Reserved Reserved, Set = 1 1 1 Reserved Reserved, Set = 1 0 1 PCIF1 PCIF1 Output Enable 0 = Disabled, 1 = Enabled Byte 3: Control Register 3 Bit @Pup Name Description 7 0 SRC7 Allow control of SRC[T/C]7 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 6 0 RESERVED 5 0 SRC5 Document #: 38-07679 Rev. ** RESERVED Allow control of SRC[T/C]5 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# Page 5 of 20 [+] Feedback CY28441 Byte 3: Control Register 3 (continued) Bit @Pup Name Description 4 0 SRC4 Allow control of SRC[T/C]4 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 3 0 SRC3 Allow control of SRC[T/C]3 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 2 0 SRC2 Allow control of SRC[T/C]2 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 1 0 SRC1 Allow control of SRC[T/C]1 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 0 0 SRC0 Allow control of SRC[T/C]0 with assertion of PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# Byte 4: Control Register 4 Bit @Pup Name 7 0 Reserved Reserved, Set = 0 Description 6 0 DOT96T/C DOT_PWRDWN Drive Mode 0 = Driven in PWRDWN, 1 = Hi-Z 5 0 Reserved 4 0 PCIF1 Allow control of PCIF1 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 3 0 PCIF0 Allow control of PCIF0 with assertion of PCI_STP# or SW PCI_STP# 0 = Free running, 1 = Stopped with PCI_STP# 2 1 CPU[T/C]2 Allow control of CPU[T/C]2 with assertion of CPU_STP# 0 = Free running, 1 = Stopped with CPU_STP# 1 1 CPU[T/C]1 Allow control of CPU[T/C]1 with assertion of CPU_STP# 0 = Free running, 1 = Stopped with CPU_STP# 0 1 CPU[T/C]0 Allow control of CPU[T/C]0 with assertion of CPU_STP# 0 = Free running, 1 = Stopped with CPU_STP# Reserved, Set = 0 Byte 5: Control Register 5 Bit @Pup Name Description 7 0 SRC[T/C][7:0] SRC[T/C] Stop Drive Mode 0 = Driven when PCI_STP# asserted,1 = Hi-Z when PCI_STP# asserted 6 0 CPU[T/C]2 CPU[T/C]2 Stop Drive Mode 0 = Driven when CPU_STP# asserted,1 = Hi-Z when CPU_STP# asserted 5 0 CPU[T/C]1 CPU[T/C]1 Stop Drive Mode 0 = Driven when CPU_STP# asserted,1 = Hi-Z when CPU_STP# asserted 4 0 CPU[T/C]0 CPU[T/C]0 Stop Drive Mode 0 = Driven when CPU_STP# asserted,1 = Hi-Z when CPU_STP# asserted 3 0 SRC[T/C][7:0] SRC[T/C] PWRDWN Drive Mode 0 = Driven when PD asserted,1 = Hi-Z when PD asserted 2 0 CPU[T/C]2 CPU[T/C]2 PWRDWN Drive Mode 0 = Driven when PD asserted,1 = Hi-Z when PD asserted 1 0 CPU[T/C]1 CPU[T/C]1 PWRDWN Drive Mode 0 = Driven when PD asserted,1 = Hi-Z when PD asserted 0 0 CPU[T/C]0 CPU[T/C]0 PWRDWN Drive Mode 0 = Driven when PD asserted,1 = Hi-Z when PD asserted Byte 6: Control Register 6 Bit @Pup 7 0 Document #: 38-07679 Rev. ** Name Description REF/N or Hi-Z Select 0 = Hi-Z, 1 = REF/N Clock Page 6 of 20 [+] Feedback CY28441 Byte 6: Control Register 6 (continued) Bit @Pup Name Description 6 0 5 0 Reserved 4 1 REF 3 1 PCIF, SRC, PCI 2 Externally selected CPUT/C FS_C Reflects the value of the FS_C pin sampled on power up 0 = FS_C was low during VTT_PWRGD# assertion 1 Externally selected CPUT/C FS_B Reflects the value of the FS_B pin sampled on power up 0 = FS_B was low during VTT_PWRGD# assertion 0 Externally selected CPUT/C FS_A Reflects the value of the FS_A pin sampled on power up 0 = FS_A was low during VTT_PWRGD# assertion Test Clock Mode Entry Control 0 = Normal operation, 1 = REF/N or Hi-Z mode, Reserved, Set = 0 REF Output Drive Strength 0 = 1X, 1 = 2X SW PCI_STP Function 0=SW PCI_STP assert, 1= SW PCI_STP deassert When this bit is set to 0, all STOPPABLE PCI, PCIF and SRC outputs will be stopped in a synchronous manner with no short pulses. When this bit is set to 1, all STOPPED PCI, PCIF and SRC outputs will resume in a synchronous manner with no short pulses. Byte 7: Vendor ID Bit @Pup Name Description 7 0 Revision Code Bit 3 Revision Code Bit 3 6 0 Revision Code Bit 2 Revision Code Bit 2 5 0 Revision Code Bit 1 Revision Code Bit 1 4 0 Revision Code Bit 0 Revision Code Bit 0 3 1 Vendor ID Bit 3 Vendor ID Bit 3 2 0 Vendor ID Bit 2 Vendor ID Bit 2 1 0 Vendor ID Bit 1 Vendor ID Bit 1 0 0 Vendor ID Bit 0 Vendor ID Bit 0 BYTE 8: CLKREQ Control Register Bit @Pup Name Description 7 0 Reserved Reserved 6 1 CLKREQ#B SRC[T/C]5 CLKREQ#B control 1 = SRC[T/C]5 stoppable by CLKREQ#B pin 0 = SRC[T/C]5 not controlled by CLKREQ#B pin 5 0 CLKREQ#B SRC[T/C]3 CLKREQ#B control 1 = SRC[T/C]3 stoppable by CLKREQ#B pin 0 = SRC[T/C]3 not controlled by CLKREQ#B pin 4 0 CLKREQ#B SRC[T/C]1 CLKREQ#B control 1 = SRC[T/C]1 stoppable by CLKREQ#B pin 0 = SRC[T/C]1 not controlled by CLKREQ#B pin 3 0 Reserved Reserved 2 1 CLKREQ#A SRC[T/C]4 CLKREQ#A control 1 = SRC[T/C]4 stoppable by CLKREQ#A pin 0 = SRC[T/C]4 not controlled by CLKREQ#A pin 1 0 CLKREQ#A SRC[T/C]2 CLKREQ#A control 1 = SRC[T/C]2 stoppable by CLKREQ#A pin 0 = SRC[T/C]2 not controlled by CLKREQ#A pin 0 0 CLKREQ#A SRC[T/C]0 CLKREQ#A control 1 = SRC[T/C]0 stoppable by CLKREQ#A pin 0 = SRC[T/C]0 not controlled by CLKREQ#A pin Document #: 38-07679 Rev. ** Page 7 of 20 [+] Feedback CY28441 Table 5. Crystal Recommendations Frequency (Fund) Cut Loading Load Cap Drive (max.) Shunt Cap (max.) Motional (max.) Tolerance (max.) Stability (max.) Aging (max.) 14.31818 MHz AT Parallel 0.1 mW 5 pF 0.016 pF 35 ppm 30 ppm 5 ppm 20 pF Crystal Recommendations Clock Chip The CY28441 requires a Parallel Resonance Crystal. Substituting a series resonance crystal will cause the CY28441 to operate at the wrong frequency and violate the ppm specification. For most applications there is a 300-ppm frequency shift between series and parallel crystals due to incorrect loading. See Table 5. Pin 3 to 6p Crystal Loading Crystal loading plays a critical role in achieving low ppm performance. To realize low ppm performance, the total capacitance the crystal will see must be considered to calculate the appropriate capacitive loading (CL). Figure 1 shows a typical crystal configuration using the two trim capacitors. An important clarification for the following discussion is that the trim capacitors are in series with the crystal not parallel. It’s a common misconception that load capacitors are in parallel with the crystal and should be approximately equal to the load capacitance of the crystal. This is not true. Ci2 Ci1 X2 X1 Cs1 Cs2 Trace 2.8pF XTAL Ce1 Ce2 Trim 33pF Figure 2. Crystal Loading Example As mentioned previously, the capacitance on each side of the crystal is in series with the crystal. This mean the total capacitance on each side of the crystal must be twice the specified load capacitance (CL). While the capacitance on each side of the crystal is in series with the crystal, trim capacitors (Ce1,Ce2) should be calculated to provide equal capacitance loading on both sides. Use the following formulas to calculate the trim capacitor values for Ce1 and Ce2. Load Capacitance (each side) Ce = 2 * CL – (Cs + Ci) Figure 1. Crystal Capacitive Clarification Total Capacitance (as seen by the crystal) Calculating Load Capacitors In addition to the standard external trim capacitors, trace capacitance and pin capacitance must also be considered to correctly calculate crystal loading. As mentioned previously, the capacitance on each side of the crystal is in series with the crystal. This means the total capacitance on each side of the crystal must be twice the specified crystal load capacitance (CL). While the capacitance on each side of the crystal is in series with the crystal, trim capacitors (Ce1,Ce2) should be calculated to provide equal capacitive loading on both sides. CLe = 1 1 ( Ce1 + Cs1 + Ci1 + 1 Ce2 + Cs2 + Ci2 ) CL ....................................................Crystal load capacitance CLe ......................................... Actual loading seen by crystal using standard value trim capacitors Ce ..................................................... External trim capacitors Cs ..............................................Stray capacitance (terraced) Ci .......................................................... Internal capacitance (lead frame, bond wires etc.) CLK_REQ[0:1]# Description The CLKREQ#[A:B] signals are active LOW input used for clean enabling and disabling selected SRC outputs. The outputs controlled by CLKREQ#[A:B] are determined by the settings in register byte 8. The CLKREQ# signal is a de-bounced signal in that it’s state must remain unchanged during two consecutive rising edges of DIFC to be recognized as a valid assertion or de-assertion. (The assertion and deassertion of this signal is absolutely asynchronous.) Document #: 38-07679 Rev. ** Page 8 of 20 [+] Feedback CY28441 . CLKREQ#X SRCT(free running) SRCC(free running) SRCT(stoppable) SRCT(stoppable) Figure 3. CLK_REQ#[A:B] Deassertion/Assertion Waveform CLK_REQ[A:B]# Assertion (CLKREQ# -> LOW) All differential outputs that were stopped are to resume normal operation in a glitch free manner. The maximum latency from the assertion to active outputs is between 2-6 SRC clock periods (2 clocks are shown) with all SRC outputs resuming simultaneously. All stopped SRC outputs will be driven HIGH within 10 ns of CLKREQ#[1:0] deassertion to a voltage greater than 200 mV. CLK_REQ[A:B]# Deassertion (CLKREQ# -> HIGH) The impact of deasserting the CLKREQ#[A:B] pins is all SRC outputs that are set in the control registers to stoppable via deassertion of CLKREQ#[A:B] are to be stopped after their next transition. The final state of all stopped DIF signals is LOW, both SRCT clock and SRCC clock outputs will not be driven. PD (Power-down) Clarification The VTT_PWRGD# /PD pin is a dual-function pin. During initial power-up, the pin functions as VTT_PWRGD#. Once VTT_PWRGD# has been sampled LOW by the clock chip, the pin assumes PD functionality. The PD pin is an asynchronous active HIGH input used to shut off all clocks cleanly prior to shutting off power to the device. This signal is synchronized internal to the device prior to powering down the clock synthesizer. PD is also an asynchronous input for powering up the system. When PD is asserted HIGH, all clocks need to be driven to a LOW value and held prior to turning off the VCOs and the crystal oscillator. PD (Power-down) – Assertion When PD is sampled HIGH by two consecutive rising edges of CPUC, all single-ended outputs will be held low on their next HIGH to LOW transition and differential clocks must held HIGH or Hi-Zd (depending on the state of the control register drive mode bit) on the next diff clock# HIGH to LOW transition within 4 clock periods. When the SMBus PD drive mode bit corresponding to the differential (CPU, SRC, and DOT) clock output of interest is programmed to ‘0’, the clock output are held with “Diff clock” pin driven HIGH at 2 x Iref, and “Diff clock#” tristate. If the control register PD drive mode bit corresponding to the output of interest is programmed to “1”, then both the “Diff clock” and the “Diff clock#” are tristate. Note Figure 4 shows CPUT = 133 MHz and PD drive mode = ‘1’ for all differential outputs. This diagram and description is applicable to valid CPU frequencies 100 and 133 MHz. In the event that PD mode is desired as the initial power-on state, PD must be asserted HIGH in less than 10 µs after asserting Vtt_PwrGd#. PD CPUT, 133MHz CPUC, 133MHz SRCT 100MHz SRCC 100MHz USB, 48MHz DOT96T DOT96C PCI, 33 MHz REF Figure 4. Power-down Assertion Timing Waveform Document #: 38-07679 Rev. ** Page 9 of 20 [+] Feedback CY28441 Tstable 200mV Figure 7. CPU_STP# Deassertion Waveform 1.8mS CPU_STOP# PD CPUT(Free Running CPUC(Free Running CPUT(Stoppable) CPUC(Stoppable) DOT96T DOT96C Figure 8. CPU_STP#= Driven, CPU_PD = Driven, DOT_PD = Driven 1.8mS CPU_STOP# PD CPUT(Free Running) CPUC(Free Running) CPUT(Stoppable) CPUC(Stoppable) DOT96T DOT96C Figure 9. CPU_STP# = Hi-Z, CPU_PD = Hi-Z, DOT_PD = tHi-Z Document #: 38-07679 Rev. ** Page 11 of 20 [+] Feedback CY28441 PCI_STP# Assertion[1] PCI_STP# Deassertion The PCI_STP# signal is an active LOW input used for synchronous stopping and starting the PCI outputs while the rest of the clock generator continues to function. The set-up time for capturing PCI_STP# going LOW is 10 ns (tSU). (See Figure 10.) The PCIF clocks will not be affected by this pin if their corresponding control bit in the SMBus register is set to allow them to be free running. The deassertion of the PCI_STP# signal will cause all PCI and stoppable PCIF clocks to resume running in a synchronous manner within two PCI clock periods after PCI_STP# transitions to a high level. (See Figure 11.) PCI_STP# Tsu PCI_F PCI SRC 100MHz Figure 10. PCI_STP# Assertion Waveform Tsu Tdrive_SRC PCI_STP# PCI_F PCI SRC 100MHz Figure 11. PCI_STP# Deassertion Waveform Note: 1. The PCI STOP function is controlled by two inputs. One is the device PCI_STP# pin number 55 and the other is SMBus byte6 bit 3. These two inputs are logically OR’ed. If either the external pin or the internal SMBus register bit is set LOW then the stoppable PCI clocks will be stopped in a logic LOW state. Document #: 38-07679 Rev. ** Page 12 of 20 [+] Feedback CY28441 FS_A, FS_B,FS_C VTT_PW RGD# PW RGD_VRM 0.2-0.3mS Delay VDD Clock Gen State 0 Clock State W ait for VTT_PW RGD# State 1 State 2 Off Clock Outputs State 3 On On Off Clock VCO Device is not affected, VTT_PW RGD# is ignored Sample Sels Figure 12. VTT_PWRGD# Timing Diagram S2 S1 Delay >0.25mS VTT_PWRGD# = Low Sample Inputs straps VDD_A = 2.0V Wait for