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COM Express® Carrier Board Design Guide

2.12

LPC Bus – Low Pin Count Interface

2.12.1 Signal Definition

Table 12: LPC Interface Signal Descriptions

Signal

Pin

Description

I/O

Comment

LPC_SERIRQ

A50

LPC serialized IRQ.

I/O 3.3V
CMOS

LPC_FRAME#

LPC frame indicates start of a new
cycle or termination of a broken
cycle.

O 3.3V
CMOS

LPC_AD0
LPC_AD1
LPC_AD2
LPC_AD3

B4
B5
B6
B7

LPC multiplexed command,
address and data.

I/O 3.3V
CMOS

LPC_DRQ0#
LPC_DRQ1#

B8
B9

LPC encoded DMA/Bus master
request.

I 3.3V
CMOS

Not all Modules support
LPC DMA. Contact your
vendor for information.

LPC_CLK

B10

LPC clock output 33MHz.

O 3.3V
CMOS

Summary of Contents for ET976

Page 1: ...COM EXPRESS CARRIER BOARD DESIGN GUIDE Version 1 0 January 2022...

Page 2: ...antee this document is error free IBASE assumes no liability for incidental or consequential damages arising from misapplication or inability to use the information contained herein nor for any infrin...

Page 3: ...3 1 DisplayPort HDMI DVI 11 2 3 1 1 Reference Schematic 12 2 3 1 2 Routing Considerations 17 2 3 2 SDVO 18 2 3 2 1 Signal Definitions 18 2 3 2 2 Reference Schematics 18 2 3 2 3 Routing Considerations...

Page 4: ...dio Interfaces 40 2 11 1 Reference Schematics 41 2 11 1 1 High Definition Audio 41 2 11 2 Routing Considerations 43 2 12 LPC Bus Low Pin Count Interface 44 2 12 1 Signal Definition 44 2 12 2 LPC Bus R...

Page 5: ...61 2 18 3 Power Management Signals 62 2 18 4 Watchdog Timer 65 2 18 5 General Purpose Input Output GPIO 65 2 18 6 Fan Connector 66 2 18 7 Thermal Interface 67 2 19 PCI Bus 68 2 19 1 Signal Definition...

Page 6: ...vi COM Express Carrier Board Design Guide 5 5 COM Express Connector Tyco This page is intentionally left blank...

Page 7: ...is given The examples shown here have been taken from the designs that were already tested For any questions that you may have in the design of carrier boards please contact IBASE sales representative...

Page 8: ...Express Graphics Digital Display Interfaces LAN USB Ports USB 3 0 SATA LVDS Embedded DisplayPort eDP VGA Digital Audio Interfaces LPC Bus Low Pin Count Interface Serial Peripheral Interface Bus Genera...

Page 9: ...General Purpose PCIe Lanes 2 1 1 Device Up Device Down and PCIe Rx Tx Coupling Capacitors Figure 1 PCIe Rx Coupling Capacitors The coupling caps for the Module PCIe TX lines are to be on the Module a...

Page 10: ...4 COM Express Carrier Board Design Guide 2 1 2 Schematic Examples Figure 2 PCI Express x1 Slot Example...

Page 11: ...COM Express Carrier Board Design Guide 5 Figure 3 PCI Express x4 Slot Example...

Page 12: ...6 COM Express Carrier Board Design Guide Figure 4 PCIe Mini Card Reference Circuitry...

Page 13: ...used 92 10 differential impedance Gen1 designs used 100 20 differential impedance New designs use 85 15 differential impedance for Gen1 Gen2 and Gen3 signaling Route the traces as differential pairs r...

Page 14: ...PCIE PEG_TX4 PEG_TX4 D65 D66 PEG channel 4 Transmit Output differential pair O PCIE Type 2 SDVOC_RED Shared with SDVOC_RED PEG_RX5 PEG_RX5 C68 C69 PEG channel 5 Receive Input differential pair I PCIE...

Page 15: ...D101 D102 PEG channel 15 Transmit Output differential pair O PCIE SDVO_I2C_CLK D73 I2C based control signal clock for SDVO device O 2 5V CMOS SDVO enabled if this line is pulled up to 2 5V on Carrier...

Page 16: ...10 COM Express Carrier Board Design Guide 2 2 1 Reference Schematics Figure 5 x1 x4 x8 x16 Slot...

Page 17: ...auxiliary lane and 1 hot plug detect signal The DDC_AUX_SEL pin should be routed to pin 13 of the DisplayPort connector to enable Dual Mode When HDMI DVI is directly done on the Carrier Board this pi...

Page 18: ...12 COM Express Carrier Board Design Guide 2 3 1 1 Reference Schematic Figure 6 DisplayPort Reference Schematics...

Page 19: ...COM Express Carrier Board Design Guide 13 Figure 7 HDMI Example 1...

Page 20: ...14 COM Express Carrier Board Design Guide Figure 7 HDMI Example 2...

Page 21: ...COM Express Carrier Board Design Guide 15 Figure 8 DVI Example 1...

Page 22: ...16 COM Express Carrier Board Design Guide Figure 8 DVI Example 2...

Page 23: ...od TMDS The TDMS differential signals between the level shifter and the DVI connector have to be routed in pairs with a differential impedance of 100 The length of the differential signals must be kep...

Page 24: ...G COM Express Carrier Board Design Guide Rev 2 0 December 6 2013 Page 59 Figure 22 DVI Example 2 3 2 3 Routing Considerations DVI is based on the differential signaling method TDMS The TDMS differenti...

Page 25: ...on I O Remarks GBE0_MDI0 GBE0_MDI0 A13 A12 Media Dependent Interface MDI differential pair 0 The MDI can operate in 1000 100 and 10Mbit sec modes I O GBE This signal pair is used for all modes GBE0_MD...

Page 26: ...to meet a specific waveform template and associated signal integrity requirements defined in the IEEE 802 3 2005 specification Routing rules should be observed on the Carrier Board The four status sig...

Page 27: ...ule USB4 A40 USB Port 4 data or D I O USB optional on Module USB4 A39 USB Port 4 data or D I O USB optional on Module USB5 B40 USB Port 5 data or D I O USB optional on Module USB5 B39 USB Port 5 data...

Page 28: ...e USB signals as differential pairs with a 90 differential impedance and a 45 single ended impedance A USB pair is routed on a single layer adjacent to a ground plane USB pairs should not cross plane...

Page 29: ...B channels 2 and 3 I CMOS Table 7 USB 3 0 Differential Lines Signal Pins Pins Description I O USB_SSTX0 D4 B23 USB Port 0 SuperSpeed TX O PCIE USB_SSTX0 D3 B22 USB Port 0 SuperSpeed TX O PCIE USB_SSTX...

Page 30: ...24 COM Express Carrier Board Design Guide 2 6 2 Reference Schematics Figure 12 USB 3 0 Example 1...

Page 31: ...COM Express Carrier Board Design Guide 25 Figure 12 USB 3 0 Example 2...

Page 32: ...ended impedance Route USB SuperSpeed signals as differential pairs with an 85 differential impedance and a 50 single ended impedance A USB pair is routed on a single layer adjacent to a ground plane U...

Page 33: ...tial pair I SATA SATA1_TX SATA1_TX B16 B17 Serial ATA channel 1 Transmit output differential pair O SATA SATA2_RX SATA2_RX A25 A26 Serial ATA channel 2 Receive input differential pair I SATA SATA2_TX...

Page 34: ...ions Route SATA signals as differential pairs with an 85 differential impedance and a 50 single ended impedance Ideally a SATA pair is routed on a single layer adjacent to a ground plane SATA pairs sh...

Page 35: ...nnel B differential signal pair 0 O LVDS LVDS_B1 LVDS_B1 B73 B74 LVDS channel B differential signal pair 1 O LVDS LVDS_B2 LVDS_B2 B75 B76 LVDS channel B differential signal pair 2 O LVDS LVDS_B3 LVDS_...

Page 36: ...30 COM Express Carrier Board Design Guide 2 8 2 Reference Schematics Figure 14 LVDS Reference Schematic 1...

Page 37: ...COM Express Carrier Board Design Guide 31 Figure 14 LVDS Reference Schematic 2...

Page 38: ...to a ground plane LVDS pairs should not cross plane splits Keep layer transitions to a minimum When needed reference LVDS pairs to a power plane The power plane must be well bypassed Length matching b...

Page 39: ...iption I O eDP_TX0 A75 eDP lane 0 TX O PCIe eDP_TX0 A76 eDP lane 0 TX O PCIe eDP_TX1 A73 eDP lane 1 TX O PCIe eDP_TX1 A74 eDP lane 1 TX O PCIe eDP_TX2 A71 eDP lane 2 TX O PCIe eDP_TX2 A72 eDP lane 2 T...

Page 40: ...34 COM Express Carrier Board Design Guide 2 9 2 Reference Schematics Figure 15 eDP Reference Schematic...

Page 41: ...ore the signal is actively driven The panel control signals eDP_BLKT_EN eDP_BLKT_CTRL as well as eDP_HPD are 3 3V level signals Pay attention to your panel specifications for correct voltage levels an...

Page 42: ...g output VGA_BLU B92 3 Blue component of analog DAC monitor output designed to drive a 37 5 equivalent load O Analog Analog output VGA_HSYNC B93 13 Horizontal sync output to VGA monitor O 3 3V CMOS VG...

Page 43: ...COM Express Carrier Board Design Guide 37 2 10 2 VGA Reference Schematics Figure 16 VGA Reference Schematics 1...

Page 44: ...38 COM Express Carrier Board Design Guide Figure 16 VGA Reference Schematics 2...

Page 45: ...ls with 5V tolerance so implement high impedance unidirectional buffers to prevent potential electrical over stress of the Module and avoid that VGA monitors may attempt to drive the monitor sync sign...

Page 46: ...3V Suspend CMOS AC HDA_SYNC A29 Serial Sample Rate Synchronization O 3 3V CMOS AC HDA_BITCLK A32 24 MHz Serial Bit Clock for HDA CODEC O 3 3V CMOS AC HDA_SDOUT A33 Audio Serial Data Output Stream O 3...

Page 47: ...COM Express Carrier Board Design Guide 41 2 11 1 Reference Schematics 2 11 1 1 High Definition Audio Figure 18 HDA Example Schematic 1...

Page 48: ...42 COM Express Carrier Board Design Guide Figure 18 HDA Example Schematic 2...

Page 49: ...e analog ground plane The split between the planes must be at least 0 05 inch wide Route analog power and signal traces over the analog ground plane Route digital power and signal traces over the digi...

Page 50: ...ized IRQ I O 3 3V CMOS LPC_FRAME B3 LPC frame indicates start of a new cycle or termination of a broken cycle O 3 3V CMOS LPC_AD0 LPC_AD1 LPC_AD2 LPC_AD3 B4 B5 B6 B7 LPC multiplexed command address an...

Page 51: ...COM Express Carrier Board Design Guide 45 2 12 2 LPC Bus Reference Schematics 2 12 2 1 Super I O Figure 19 LPC Super I O Example 1...

Page 52: ...46 COM Express Carrier Board Design Guide Figure 19 LPC Super I O Example 2...

Page 53: ...milar to PCI signals Route the LPC bus as 55 single ended signals The bus preferably should be referenced to ground or to a well bypassed power plane or a combination of the two Point to point daisy c...

Page 54: ...ier Board SPI sourced from Module nominally 3 3V The Module shall provide a minimum of 100mA on SPI_POWER Carriers shall use less than 100mA of SPI_POWER SPI_POWER shall only be used to power SPI devi...

Page 55: ...9 2 13 2 SPI Reference Schematics Figure 21 SPI Reference Schematics 2 13 3 Routing Considerations The SPI signals SPI_MISO SPI_MOSI SPI_CS and SPI_CLK should be routed with a maximum length of 4 5 an...

Page 56: ...line I O OD CMOS 3 3V Suspend 2 14 2 Reference Schematics Figure 22 System Configuration EEPROM Circuitry 2 14 3 Connectivity Considerations The maximum capacitance allowed on the Carrier General Pur...

Page 57: ...COM Express Carrier Board Design Guide 51 2 15 System Management Bus SMBus Figure 23 System Management Bus Separation...

Page 58: ...ta line I O OD CMOS 3 3V Suspend rail SMB_ALERT B15 System Management Bus Alert I CMOS 3 3V Suspend Rail 2 15 2 Routing Considerations The SMBus should be connected to all or none of the PCIe PCI devi...

Page 59: ...gnal Definition Signal Pin Description I O SER0_TX A98 Transmit Line for Serial Port 0 O CMOS protected SER0_RX A99 Receive Line for Serial Port 0 I CMOS protected SER1_TX A101 Transmit Line for Seria...

Page 60: ...54 COM Express Carrier Board Design Guide 2 16 2 Reference Schematics 2 16 2 1 General Purpose Serial Port Example Figure 24 General Purpose Serial Port Example 1...

Page 61: ...COM Express Carrier Board Design Guide 55 Figure 24 General Purpose Serial Port Example 2...

Page 62: ...ations that need to be taken 2 17 CAN Interface 2 17 1 Signal Definitions Table 17 CAN Interface Signal Definition Signal Pin Description I O CAN_TX A101 Transmit Line for CAN can be shared with SER1...

Page 63: ...COM Express Carrier Board Design Guide 57 2 17 2 Reference Schematics Figure 25 CAN Bus Example 1...

Page 64: ...hould be routed as a differential pair signal with 120 Ohm differential impedance The end points of CAN bus should be terminated with 120 Ohms or with 60 Ohms from the CAN_H line and 60 Ohms from the...

Page 65: ...signal of the Module used by an external keyboard controller to force a system reset I 3 3V CMOS Only Available on T1 T5 KBD_A20GATE A87 Input signal of the Module used by an external keyboard control...

Page 66: ...60 COM Express Carrier Board Design Guide 2 18 1 Speaker Output Figure 26 Speaker Output Circuitry...

Page 67: ...COM Express Carrier Board Design Guide 61 2 18 2 RTC Battery Implementation Figure 27 RTC Battery Circuitry with Serial Schottky Diode...

Page 68: ...he current system state and context is stored in main memory and all unnecessary system logic is turned off Only main memory and logic required to wake up the system remain powered by the Suspend volt...

Page 69: ...operating voltages are within the ranges required for proper operation I 3 3V CMOS SUS_STAT B18 Suspend status signal to indicate that the system will be entering a low power state soon It can be use...

Page 70: ...64 COM Express Carrier Board Design Guide Figure 28 PWRBTN and SYS_RESET Circuitry...

Page 71: ...rpose input pins Pulled high internally on the Module I 3 3V CMOS GPI3 A85 General purpose input pins Pulled high internally on the Module I 3 3V CMOS GPO0 A93 General purpose output pins Upon a hardw...

Page 72: ...66 COM Express Carrier Board Design Guide 2 18 6 Fan Connector Figure 31 Fan Connector Reference Schematic...

Page 73: ...Thermal Alarm active low signal generated by the external hardware to indicate an over temperature situation This signal can be used to initiate thermal throttling I 3 3V CMOS THRMTRIP A35 Thermal Tr...

Page 74: ...a lines I O 3 3V PCI_AD18 D38 PCI bus multiplexed address and data lines I O 3 3V PCI_AD19 C40 PCI bus multiplexed address and data lines I O 3 3V PCI_AD20 D39 PCI bus multiplexed address and data lin...

Page 75: ...output line active low O 3 3V PCI_RESET C23 PCI Reset output active low O 3 3V_SBY Asserted during system reset PCI_LOCK C35 PCI Lock control line active low I O 3 3V PCI_SERR D33 System Error SERR ma...

Page 76: ...CI Bus Interrupt Routing Device Signal Slot Device 1 Slot Device 2 Slot Device 3 Slot Device 4 IDSEL PCI_AD 20 PCI_AD 21 PCI_AD 22 PCI_AD 23 INTA PCI_IRQ A PCI_IRQ B PCI_IRQ C PCI_IRQ D INTB if used P...

Page 77: ...Design Guide 71 2 19 3 1 Device Down Example Figure 33 PCI Device Down Example Dual UART Please refer to PICMG COM Express Carrier Board Design Guide Rev 2 0 December 6 2013 Page 150 Figure 60 PCI Dev...

Page 78: ...C12 Bidirectional data to from IDE device I O 3 3V 16 16 30 IDE_D15 C5 Bidirectional data to from IDE device I O 3 3V 18 18 31 IDE_A 0 2 D13 D15 Address lines to IDE device O 3 3V 35 33 36 35 33 36 2...

Page 79: ...rd Design Guide 73 Figure 34 IDE 40 Pin and CompactFlash 50 Pin Connector Please refer to PICMG COM Express Carrier Board Design Guide Rev 2 0 December 6 2013 Page 155 Figure 63 IDE 40 Pin and Compact...

Page 80: ...74 COM Express Carrier Board Design Guide Chapter 3 Power and Reset The information provided in this chapter includes...

Page 81: ...COM Express Carrier Board Design Guide 75 3 1 ATX Style Power Control 3 2 Reference Schematics Figure 35 AT and ATX Power Supply 1...

Page 82: ...5V 3 3V and 12V outputs are all present and OK to use 12V1DC 12V power rail for use by all system components except for the CPU controlled by 12V2DC 12V power rail for use by the CPU controlled by PS_...

Page 83: ...oad is recommended K eep the Carrier Board VCC_12 trace short wide and away from other parts of the Carrier Board If there are layer transitions in the power delivery path use redundant power vias via...

Page 84: ...78 COM Express Carrier Board Design Guide Chapter 4 Carrier Board PCB Layout Guidelines...

Page 85: ...igure 36 Four Layer Stack up The figure above is an example of a four layer stack up Layers L1 and L4 are used for signal routing Layers L2 and L3 are used for solid ground and power planes respective...

Page 86: ...f a six layer stack up Layers L1 L3 L4 and L6 are used for signal routing Layers L2 and L5 are power and ground planes respectively Microstrips on Layers 1 and 6 reference solid ground and power plane...

Page 87: ...e solid ground planes while L4 and L5 are used for power Microstrip Layers 1 and 8 reference solid ground planes on Layers 2 and 7 respectively Inner signal Layers 3 and 6 are asymmetric striplines th...

Page 88: ...82 COM Express Carrier Board Design Guide 4 3 Trace Impedance Considerations Figure 39 Stackup Impedance...

Page 89: ...M Express Carrier Board Design Guide 83 Chapter 5 Mechanical Considerations 5 1 Form Factors Figure 40 Mechanical comparison of available COM Express Form Factors All dimensions are shown in millimete...

Page 90: ...84 COM Express Carrier Board Design Guide 5 2 Heatspreader Figure 41 IBASE HSET976 1 Heatspreader Figure 42 Side View of Heatspreader COM Express Module Carrier board layer...

Page 91: ...COM Express Carrier Board Design Guide 85 5 3 COM Express Carrier Board Figure 43 IBASE IP413 COM Express Carrier Board...

Page 92: ...86 COM Express Carrier Board Design Guide 5 4 COM Express Module and Heatsink Figure 44 IBASE ET976 and Heatsink...

Page 93: ...COM Express Carrier Board Design Guide 87 5 5 COM Express Connector Tyco Figure 45 Tyco 220 pin COM Express Connector Pitch 0 5mm H 8mm...

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