PCI Bus Pin Out, [Parallel Bus]

PCI Bus pinout for both 32 bit and 64 bit cards is shown below;
Signal Pins 63-94 are only used on 64 bit PCI bus cards. The PCI pinout for the 32 bit bus stops at the key-way [Spacer], while the 64 bit pin out occupies the entire table. The PCI local bus was used in personal computers to provide expansion slots for add-on cards to the motherboard.
The PCI bus replaced the ISA PC-AT expansion slot in PCs.
The PCI local bus is not the same as the new PCI Express bus which has a completely different pinout.

Peripheral Component Interface Pinout

The number sign in the pinout table below refers to: "A # symbol at the end of a signal name indicates that the signal’s asserted state occurs when it is at a low voltage. The absence of a # symbol indicates that the signal is asserted at a high voltage.

PCI Bus PinOut
Pin # Name PCI Pin Description Pin # Name PCI Pin Description
A1 TRST Test Logic Reset [JTAG Bus] B1 -12V -12 VDC
A2 +12V +12 VDC B2 TCK Test Clock [JTAG Bus]
A3 TMS Test Mode Select [JTAG Bus] B3 GND Ground
A4 TDI Test Data Input [JTAG Bus] B4 TDO Test Data Output [JTAG Bus]
A5 +5V +5 VDC B5 +5V +5 VDC
A6 INTA Interrupt A B6 +5V +5 VDC
A7 INTC Interrupt C B7 INTB Interrupt B
A8 +5V +5 VDC B8 INTD Interrupt D
A9 --- Reserved B9 PRSNT1 Present
A10 +5V Power (+5 V or +3.3 V) B10 --- Reserved
A11 --- Reserved B11 PRSNT2 Present
A12 GND03 Ground or Keyway for 3.3/Universal PWB B12 GND Ground or Keyway for 3.3/Universal PWB
A13 GND05 Ground or Key-way for 3.3/Universal PWB B13 GND Ground or Open (Key) for 3.3/Universal PWB
A14 3.3Vaux -- B14 RES Reserved
A15 RESET Reset B15 GND Ground
A16 +5V Power (+5 V or +3.3 V) B16 CLK Clock
A17 GNT Grant PCI use B17 GND Ground
A18 GND08 Ground B18 REQ Request
A19 PME# Power Management Event B19 +5V Power (+5 V or +3.3 V)
A20 AD30 Address/Data 30 B20 AD31 Address/Data 31
A21 +3.3V01 +3.3 VDC B21 AD29 Address/Data 29
A22 AD28 Address/Data 28 B22 GND Ground
A23 AD26 Address/Data 26 B23 AD27 Address/Data 27
A24 GND10 Ground B24 AD25 Address/Data 25
A25 AD24 Address/Data 24 B25 +3.3V +3.3VDC
A26 IDSEL Initialization Device Select B26 C/BE3 Command, Byte Enable 3
A27 +3.3V03 +3.3 VDC B27 AD23 Address/Data 23
A28 AD22 Address/Data 22 B28 GND Ground
A29 AD20 Address/Data 20 B29 AD21 Address/Data 21
A30 GND12 Ground B30 AD19 Address/Data 19
A31 AD18 Address/Data 18 B31 +3.3V +3.3 VDC
A32 AD16 Address/Data 16 B32 AD17 Address/Data 17
A33 +3.3V05 +3.3 VDC B33 C/BE2 Command, Byte Enable 2
A34 FRAME Address or Data phase B34 GND13 Ground
A35 GND14 Ground B35 IRDY# Initiator Ready
A36 TRDY# Target Ready B36 +3.3V06 +3.3 VDC
A37 GND15 Ground B37 DEVSEL Device Select
A38 STOP Stop Transfer Cycle B38 GND16 Ground
A39 +3.3V07 +3.3 VDC B39 LOCK# Lock bus
A40 SMBCLK SMB CLK [SMbus Description] B40 PERR# Parity Error
A41 SMBDAT SMB DATA [SMbus Description] B41 +3.3V08 +3.3 VDC
A42 GND17 Ground B42 SERR# System Error
A43 PAR Parity B43 +3.3V09 +3.3 VDC
A44 AD15 Address/Data 15 B44 C/BE1 Command, Byte Enable 1
A45 +3.3V10 +3.3 VDC B45 AD14 Address/Data 14
A46 AD13 Address/Data 13 B46 GND18 Ground
A47 AD11 Address/Data 11 B47 AD12 Address/Data 12
A48 GND19 Ground B48 AD10 Address/Data 10
A49 AD9 Address/Data 9 B49 GND20 Ground
A50 Keyway Open or Ground for 3.3V PWB B50 Keyway Open or Ground for 3.3V PWB
A51 Keyway Open or Ground for 3.3V PWB B51 Keyway Open or Ground for 3.3V PWB
A52 C/BE0 Command, Byte Enable 0 B52 AD8 Address/Data 8
A53 +3.3V11 +3.3 VDC B53 AD7 Address/Data 7
A54 AD6 Address/Data 6 B54 +3.3V12 +3.3 VDC
A55 AD4 Address/Data 4 B55 AD5 Address/Data 5
A56 GND21 Ground B56 AD3 Address/Data 3
A57 AD2 Address/Data 2 B57 GND22 Ground
A58 AD0 Address/Data 0 B58 AD1 Address/Data 1
A59 +5V Power (+5 V or +3.3 V) B59 VCC08 Power (+5 V or +3.3 V)
A60 REQ64 Request 64 bit B60 ACK64 Acknowledge 64 bit
A61 VCC11 +5 VDC B61 VCC10 +5 VDC
A62 VCC13 +5 VDC B62 VCC12 +5 VDC
64 bit spacer KEYWAY
64 bit spacer KEYWAY
A63 GND Ground B63 RES Reserved
A64 C/BE[7]# Command, Byte Enable 7 B64 GND Ground
A65 C/BE[5]# Command, Byte Enable 5 B65 C/BE[6]# Command, Byte Enable 6
A66 +5V Power (+5 V or +3.3 V) B66 C/BE[4]# Command, Byte Enable 4
A67 PAR64 Parity 64 B67 GND Ground
A68 AD62 Address/Data 62 B68 AD63 Address/Data 63
A69 GND Ground B69 AD61 Address/Data 61
A70 AD60 Address/Data 60 B70 +5V Power (+5 V or +3.3 V)
A71 AD58 Address/Data 58 B71 AD59 Address/Data 59
A72 GND Ground B72 AD57 Address/Data 57
A73 AD56 Address/Data 56 B73 GND Ground
A74 AD54 Address/Data 54 B74 AD55 Address/Data 55
A75 +5V Power (+5 V or +3.3 V) B75 AD53 Address/Data 53
A76 AD52 Address/Data 52 B76 GND Ground
A77 AD50 Address/Data 50 B77 AD51 Address/Data 51
A78 GND Ground B78 AD49 Address/Data 49
A79 AD48 Address/Data 48 B79 +5V Power (+5 V or +3.3 V)
A80 AD46 Address/Data 46 B80 AD47 Address/Data 47
A81 GND Ground B81 AD45 Address/Data 45
A82 AD44 Address/Data 44 B82 GND Ground
A83 AD42 Address/Data 42 B83 AD43 Address/Data 43
A84 +5V Power (+5 V or +3.3 V) B84 AD41 Address/Data 41
A85 AD40 Address/Data 40 B85 GND Ground
A86 AD38 Address/Data 38 B86 AD39 Address/Data 39
A87 GND Ground B87 AD37 Address/Data 37
A88 AD36 Address/Data 36 B88 +5V Power (+5 V or +3.3 V)
A89 AD34 Address/Data 34 B89 AD35 Address/Data 35
A90 GND Ground B90 AD33 Address/Data 33
A91 AD32 Address/Data 32 B91 GND Ground
A92 RES Reserved B92 RES Reserved
A93 GND Ground B93 RES Reserved
A94 RES Reserved B94 GND Ground

Designer note; the pinout provided on this page relates to the PCI main board connector on the mother board.
Add-in cards [daughter boards may have a slightly different connector pin out.

Internal Buses on the PCI Bus
Address/Data Bus: 64bit Address; 64bit Data, Time Multiplexed
System Bus: 2bits; Clock/Reset
Interface Control Bus: 7bits; Ready, Acknowledge, Stop
Parity Bus: 2 bits, 1 for the 32 LSBs and 1 for the 32 MSB bits
Errors Bus: 2 bits, 1 for Parity and 1 for System
Command/Byte Enable: 8 bits (0-3 @ 32bit, and 4-7@ 64bit Bus)
64MHz Control: 6 bits; (2) Enable/Running, (2) Present, (2) Ack/Req
Cache Size: 2 Bits
Interrupt bus: 4 bits [INTA#, INTB#, INTC#, INTD#]
JTAG Serial Bus: 5 Bits [JTAG Signal Description]
Power Supply: +5, +3.3, +12, -12v, GND

Dimensions for 3.3 volt PCI Connector for the Desk Top Personal Computer
PCI Connector Dimensions

RST# [input] Reset is used to bring PCI-specific registers, sequencers, and signals to a consistent state.

CLKRUN# [input] [Open Drain, Tri-state] Clock running is an optional signal used as an input for a device to determine the status of CLK.

M66EN [input] The 66MHZ_ENABLE pin indicates to a device whether the bus segment is operating at 66MHz or 33 MHz.

AD[31::00] [Tri-state] Address and Data are multiplexed on the same PCI pins. A bus transaction consists of an address phase followed by one or more data phases. The Time Multiplexed Address and Data bus may exist as either 0 to 31 bits (32bits) or 0 to 63 bits (64bits) using the 64 bit expansion bus. Both the Address and Data line use the same bus, Address first then Data. 32 bit PCI may also use 64 bit addressing by using two address cycles; termed Dual Address Cycles (DAC), the low order address is sent first. Additional control bits are utilized once the bus is increased to 64 bits.

PME# The Power Management Event signal is an optional signal that can be used by a device to request a change in the device or system power state.

FRAME# [Sustained Tri-State] Cycle Frame is driven by the current master to indicate the beginning and duration of an access.

IRDY# [Sustained Tri-State] Initiator Ready indicates the initiating agent's (bus master's) ability to complete the current data phase of the transaction. IRDY# is used in conjunction with TRDY#.

TRDY# [Sustained Tri-State] Target Ready indicates the target agent's (selected device's) ability to complete the current data phase of the transaction. TRDY# is used in conjunction with IRDY#.

STOP# [Sustained Tri-State] Stop indicates the current target is requesting the master to stop the current transaction.

LOCK# [Sustained Tri-State] Lock indicates an atomic operation to a bridge that may require multiple transactions to complete. When LOCK# is asserted, non-exclusive transactions may proceed to a bridge that is not currently locked.

INT# [Open Drain] Interrupts on PCI are optional and are "level sensitive," asserted low (negative true).

PAR [Tri-state] Parity is even parity across AD[31::00] and C/BE[3::0]#. Parity generation is required by all PCI agents. PAR is stable and valid one clock after each address phase.

PERR# [Sustained Tri-State] Parity Error is only for the reporting of data parity errors. Two Parity lines are made available, one for the 32 bit bus width (bits 0 to 31) and an additional one for the 64 bit expansion (bits 32 to 63). Two error bits; I assume, 1 for the LSB 32 bits and one for the upper 32 bits.

REQ# [Tri-state] Request indicates to the arbiter that this agent desires use of the bus. This is a point-to-point signal. Every master has its own REQ# line.

GNT# [Tri-state] Grant indicates to the agent that access to the bus has been granted. The GNT line is a point-to-point signal, each master has its own GNT# signal.

IDSEL [input] Initialization Device Select is used as a chip select during configuration read and write transactions.

DEVSEL# [Sustained Tri-State] Device Select, when actively driven, indicates the driving device has decoded its address as the target of the current access.

SERR# [Open Drain] System Error is for reporting address parity errors, data parity errors on the Special Cycle command, or any other system error.

C/BE[3::0]# [Tri-state] Bus Command and Byte Enables are multiplexed on the same PCI pins. During the address phase of a transaction, C/BE[3::0]# define the bus command.

The specification defines both a Reset line and a Clock line. The Clock may be either 33MHz or 66MHz. I believe the 66MHz clock rate is only defined for the 64bit bus width.
A number of 'Handshake' lines exist to allow communication, i.e. Ready, and Acknowledge, see pin out above.

JTAG The JTAG interface is optional on the PCI bus. Add-in cards [expansion boards] that do not implement the JTAG Boundary Scan are required to connect [short] TDI and TDO (pins 4A and 4B) so the scan chain is not broken.

The pinout listings showing (+5 V or +3.3 V) mean: In a +5 volt system the pins are +5 volts, in a +3.3 volt system the pins are +3.3 volts.

64-Bit Bus Extension
PCI supports a high 32-bit bus, referred to as the 64-bit extension to the standard low 32-bit bus.
The high 32-bit extension for 64-bit devices needs an additional 39 signal pins: REQ64#, ACK64#, AD[63::32], C/BE[7::4]#, and PAR64.

PAR64 Parity bit, even parity. Parity generation is required by all PCI agents. PAR is stable and valid one clock after each address phase. PAR64 covers AD[63::32] and C/BE[7::4]# and has the same timing and function as the PAR bit. PAR64 requires a pull-up resistor when 32-bit transactions are used. When PAR64 is not used the line will float to the threshold level causing oscillation or high power drain through the input buffer.

REQ64# [Request-64] is bused to all devices on the system board (including PCI connector slots) that support a 64-bit data path and indicate that the Bus Master wants to make a 64-bit transfer. This signal has a single pull-up resistor on the system board.

ACK64# [Acknowledge 64-bit Transfer] is bused to all 64-bit devices and slots on the system board and pulled up with a single resistor located on the system board. ACK64# is actively driven by the device that has positively decoded its address as the target of the current access, indicating that the target is willing to transfer data using 64 bits.

AD[63::32], Note these are Tri-state lines and require a pull-up resistor during 32-bit transactions to keep the nets from floating. The upper Address and Data bits are multiplexed on the same pins and provide 32 additional bits. During an address phase (when using the DAC command and when REQ64# is asserted), the upper 32-bits of a 64-bit address are transferred; otherwise, these bits are reserved.

C/BE[7::4]#, [Bus Command and Byte Enable] Note these lines Tri-state and require a pull-up resistor during 32-bit transactions to keep the nets from floating. The Bus Command and Byte Enable lines are multiplexed on the same pins. During an address phase (when using the DAC command and when REQ64# is asserted), the actual bus command is transferred on C/BE[7::4]#; otherwise, these bits are reserved and indeterminate. During a data phase, C/BE[7::4]# are Byte Enables indicating which byte lanes carry meaningful data when a 64-bit transaction has been negotiated by the assertion of REQ64# and ACK64#.

Back to the main PCI Bus page, or the PCI Board Dimension page PCI Card Size or Personal Computer bus page.

PRSNT[1::2]# Add-in card Present
Note; PRSNT1 [B9] and PRSNT2 [B11] are present detect pins used just to detect the presence or absence of a PCI card. The PRSNT# pins relate only to the PCI connector.

Mother boards must decouple both of these pins individually to ground with 0.01 uF capacitors, because one or both of the pins also provide an AC return path. These pins may not be bused or connected to each other on the system board. Further the PRSNT# pins on the system board is optional. If the system board design accesses these pins to obtain add-in card information, each pin must have an appropriate pull-up resistor (of approximately 5 k ohm) on the system board.

OpenOpenNo add in card present
GroundOpenAdd in card present, 25 watts max
OpenGroundAdd in card present, 15 watts max
GroundGroundAdd in card present, 7.5 watts max

Description of PCI pins and signal names'

The Peripheral Component Interface 'PCI' Bus was originally developed as a local bus expansion for the PC (ISA) bus. The PCI spec defines the Electrical requirements for the interface. No bus terminations are specified, the bus relies on signal reflection to achieve level threshold. The first version of the PCI bus ran at 33MHz with a 32 bit bus (133MBps), the current version runs at 66MHz with a 64 bit bus. The PCI bus operates either synchronously or asynchronously with the mother board bus rate. While operating asynchronously the bus will operate at any frequency from 66MHz down to (and including) 0Hz. Flow control is added to allow the bus to operate with slower devices on the bus, allowing the bus to operate at their speed. PCI is an unterminated bus, the signal relay on signal reflections to attain there final value.

PC motherboard

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Modified 3/05/12
Copyright © 1998 - 2012 All rights reserved Leroy Davis