Introduction to PCI System
Architecture
Introduction to PCI System
Direct-Connect Approach(VESA)
Main memory
CPU Local Bus Cache Memory Bus
Local Bus
Device Expansion
Bridge
Local Bus Design Constraint:
1. Redesign is necessary for Expansion Bus
next generation processor.
2. Only one local device is X-Bus Buffer
permitted. Expansion
Connectors
3. Design of local bus inter
-face is difficult.
X-Bus
4. Transfer with one device
is not permitted while the
local bus is involved in a
transfer with another I/O Device I/O Device I/O Device
device.
Buffered Approach(VESA)
CPU Local Bus Cache Memory Bus
Bus Buffer Expansion
Bridge
Buffered Local Bus Expansion Bus
I/O I/O I/O X-Bus Buffer
Device Device Device
X-Bus
A maximum of three local
bus devices can be placed on
the buffered local bus. I/O Device I/O Device I/O Device
Workstation Approach(PCI)
Main Video
Memory
Memory
CPU CPU Local Bus Host/PCI
Memory Bus
Cache/Bridge
Motion
Audio Video
Peripheral
Peripheral
PCI Bus
LAN Expansion Bus Graphics
SCSI Host Adapter Bridge
Bus Adapter Adapter
LAN
Video Frame Buffer
SCSI BUS
Disk
Expansion Bus
Tape
Bus I/O Memory
CD Master Slave Slave
ROM
Transfer Rate Comparison:
Bus Bus Frequency Transfer Transfer Rate
ISA 8.33 MHz 2 byte / 2 clock 8.33 MB/s
EISA 8.33 MHz 4 byte / 1 clock 33 MB/s
( Burst Mode)
VESA 33 MHz 4 byte / 1 clock 132 MB/s
( Read, Burst )
4 byte / 2 clock 66 MB/s
( Write, Burst )
PCI 33 MHz 4 byte / 1 clock 132 MB/s
8 byte / 1 clock 264 MB/s
66 MHz 4 byte / 1 clock 264 MB/s
8 byte / 1 clock 528 MB/s
( Burst Mode )
• PCI: Peripheral Component Interconnect
• Major PCI Revision 2.1 Features
Processor Independence
Support for up to 256 PCI functions per PCI bus
Low power consumption ( Draw as little current as possible )
Burst used for all read and write transfers
Supports 66 MHz operation, 64bit bus width
Fast access ( 60ns at bus speed 33 MHz )
Concurrent bus operation
Bus master support
Hidden bus arbitration
Low pin count ( Initiator:49pins, Target:47 pins )
Transaction integrity check( Parity check)
Three address spaces ( Memory, I/O, Configuration )
Auto configuration( Configuration register )
Software Transparency
PCI-Compliant Device Signals For Slave only
For Master only
Required Signals Optional Signals
AD[31:00] AD[63:32]
Address/Data
and Command 64-bit
C/BE[3:0]# PCI C/BE[7:4]#
Extension
COMPLIANT
PAR PAR64
DEVICE
REQ64#
FRAM# ACK64#
TRDY# LOCK#
Interface Atomic Access
IRDY#
Control STOP# INTA#
DEVSEL# INTB#
INTC#
Interrupt
IDSEL Request
INTD#
Error PERR# CLKRUN# Clock Control
Reporting SERR# SBO# Snoop
REQ# SDON
Arbitration Result
GNT# TDI
TDO
CLK TCK
System RST#
JTAG
TMS
TRST#
PCI Bus Arbitration
Initiator/ Target
Initiator ( Master ): The device that initiates a transfer
Target ( Slave ): The device that currently addressed by the initiator for
the purpose of performing a data transfer
PCI
Arbiter
GNT0#
GNT1# GNT2# GNT3#
REQ0# REQ1# REQ2# REQ3#
PCI PCI PCI PCI
Device Device Device Device
MASTER
Address, Command/
PCI Data, Byte Enables/ Bridge DRAM
Device
Parity
SLAVE SLAVE SLAVE
PCI Bus Arbitration Algorithm
First Group
Master A Master X
Second
Master B Group Master Y Master Z
A B X A B Y A B Z A B X
• Fairness ( fixed, rotational )
• Bus Parking( on specified master, on last master that acquired the bus )
• Hidden Bus Arbitration( REQ#, GNT#)
• LT ( Latency Timer ): The minimum amount of time that the bus master is
permitted to retain ownership of the bus
Example of PCI Bus Arbitration Between Two Masters
( Master B has higher priority than Master A)
1 2 3 4 5 6 7 8 9 10 11 12
CLK
REQA#
( Master A -> Arbiter )
REQB#
( Master B -> Arbiter )
GNTA#
( Arbiter -> Master A )
GNTB#
( Arbiter -> Master B )
LT not expired
FRAME#
( Master -> Target )
IRDY#
( Master -> Target )
TRDY#
( Target -> Master )
AD ADDRESS DATA DATA DATA ADDRESS DATA ADDRESS DATA
( Master Target )
A B A
Arbitration for Fast Back-To-Back Accesses
1 2 3 4 5 6 7 8
CLK
REQ#-
GNT#
FRAME#
AD ADDRESS DATA ADDRESS DATA
IRDY#
TRDY#
DEVSEL#
Delayed Transaction
Delayed Transaction
Request Phase: Target latches the request and issues retry
Completion Phase: Transaction completes on the target bus
MTXC Target cannot respond within 16 clocks:
Master
1. Address, Command, Byte Enables latched by PIIX4
2. Retry issued to MTXC
Target PIIX4 ( Request Phase )
3. Requested data fetched in buffer ( Completion Phase )
4. Master Retries the transaction with the
ISA same address, command, data
Device
OR no Retry within 215 clocks Discard the data
Commands That can Use Delayed Transactions
Interrupt Acknowledge
I/O Read
I/O Write
Memory Read
Memory Read Line
Memory Read Multiple
Configuration Read
Configuration Write
The PCI Commands
PCI Command Types
C/BE#[3:0] is used to indicate the command or
transaction type during the address phase
C/BE[3::0]# Command Type
0000 Interrupt Acknowledge
0001 Special Cycle
0010 I/O Read
0011 I/O Write
0100 Reserved
0101 Reserved
0110 Memory Read
0111 Memory Write
1000 Reserved
1001 Reserved
1010 Configuration Read
1011 Configuration Write
1100 Memory Read Multiple
1101 Dual Address Cycle
1110 Memory Read Line
1111 Memory Write and Invalidate
PCI Interrupt Acknowledge Transaction
1 2 3 4 5
CLK
FRAME #
( Host Bridge -> INT Controller )
AD Stable VECTOR
Pattern
( Host Bridge INT Controller )
C/BE # Byte Enables
INT ACK CMD
( Host Bridge -> INT Controller )
IRDY #
TRDY #
DEVSEL #
( INT Controller-> Host Bridge )
GNT #
Message Code Message Type
( on AD[15:0] The Special Cycle Transaction( Halt / Shut Down)
0000h Shut Down
Terminated with Master Abort
0001h Halt
0002h x86-specific
1 2 3 4 5 6 7 8
message
CLK
0003h-ffffh Reserved
FRAME#
• For an initiator to
Stable
broad- cast a message AD[31:0] Pattern Message
to one or more targets.
C/BE#[3:0] Special Byte
Cmd Enables
• Message type
on AD[15:0] IRDY#
• Message-dependent
TRDY#
data field on AD[31:16]
DEVSEL#
• Byte Enable on
C/BE#[3:0] GNT#
7 clocks
The Read and Write Transfers
Read Transaction
( 33.33 Mb/s )
CLK
1 2 3 4 5 6 7 8 9
FRAME#
Wait state for bus ownership
AD ADDRESS DATA-1 DATA-2 DATA-3
C/BE#
BUS CMD BYTE ENABLES BYTE ENABLES BYTE ENABLES
IRDY#
One more clock before
initiator ready to receive data
TRDY# Avoid bus
contention
Some time is needed for
fetching data
DEVSEL#
ADDRESS DATA DATA DATA
PHASE PHASE PHASE PHASE
Optimized Read Transaction
( 132 Mb/s)
1 2 3 4 5 6 7 8
Burst Transfer: CLK
1. If target memory is
cacheable. FRAME#
2. If target memory is AD Address Data1 Data2 Data3
prefetchable
BUS Byte Byte
C/BE# Byte Enables Enables Enables
CMD
IRDY#
TRDY#
DEVSEL#
GNT#
Write Transaction
( 44.44 Mb/s )
CLK
1 2 3 4 5 6 7 8 9
FRAME#
AD ADDRESS DATA-1 DATA-2 DATA-3
C/BE#
BUS CMD Byte EN Byte EN BYTE ENABLES
IRDY#
TRDY#
DEVSEL#
Optimized Write Transaction
( 132 Mb/s)
1 2 3 4 5 6 7 8
CLK
FRAME#
AD Address Data1 Data2 Data3
BUS Byte Byte Byte
C/BE# Enables Enables Enables
CMD
IRDY#
TRDY#
DEVSEL#
GNT#
Addressing
• Addressing Sequence During Memory Burst
Linear ( or Sequential ) address mode
Cache Line wrap mode
AD1 AD0 Addressing Sequence
0 0 Linear
0 1 Reserved
1 0 Cacheline wrap
1 1 Reserved
• PCI I/O Addressing
AD[31:2] : Target DW of I/O space
AD[1:0] : The Least-significant byte within the DW that the
initiator wishes to transfer with ( 00 = byte 0, 01 = byte 1 )
64 bit PCI Extension
REQ64#, ACK64#, PAR64,
AD[64::32], C/BE[7::4]
64-bit Read Request with 64-bit Transfer
CLK 1 2 3 4 5 6 7 8 9
FRAME#
REQ64#
AD[31::00] ADDRESS DATA-1 DATA-3 DATA-5
AD[63::32] DATA-2 DATA-4 DATA-6
C/BE[3::0]# BUS CMD BE# ‘s
C/BE[7::4]# BE# ‘s
IRDY#
TRDY#
DEVSEL#
ACK64#
64-bit Write Request with 32-bit Transfer
CLK 1 2 3 4 5 6 7 8 9
FRAME#
REQ64#
ADDRESS DATA-1 DATA-2 DATA-3
AD[31::00]
DATA-2
AD[63::32]
BUS CMD BE# ‘s-1 BE# ‘s-2 BE# ‘s-3
C/BE[3::0]#
BE# ‘s-2
C/BE[7::4]#
IRDY#
TRDY#
DEVSEL#
ACK64#
64-bit Dual Address Read Cycle
CLK 1 2 3 4 5 6 7 8
FRAME#
AD[31::00] LO-ADDR HI-ADDR DATA-1 DATA-3
C/BE[3::0]# DUAL AD BUS CMD BE# [3::0]
AD[63::32] HI-ADDR DATA-2 DATA-4
C/BE[7::4]# BUS CMD BE# [7::4]
IRDY#
TRDY#
DEVSEL#
REQ64#
ACK64#
Premature Transaction Termination
Master Initiated Termination
Reasons
Transaction completed normally ( Not premature transaction termination )
Initiator been preempted ( GNT# removed )
Preemption during timeslice by another bus master
Timeslice expiration followed by preemption
Master abort
No target respond to the address ( DEVSEL# not asserted)
No device resides at the address
Special cycle
Configuration accessing a non-existent target
Preemption
1 2 3 4 5 6 7
Example
CLK
Preempted
GNT#
FRAME#
Internal LT time out sensed
IRDY#
TRDY#
Timer CLK
Expiration
Example GNT#
Preempted
FRAME#
Time out sensed
IRDY#
TRDY#
Example of Master-abort on Single-Data
Phase Transaction
1 2 3 4 5 6 7 8
CLK
FRAME#
IRDY#
TRDY#
DEVSEL# Fast Medium Slow Bridge
Master Abort : Target doesn’t claim transaction
Target Initiated Termination( STOP# )
Disconnect
Reasons
Target slow to complete a data phase which is neither the first nor
the final data phase ( more than 8 PCI clocks )
Targets don’t support burst mode
Memory target doesn’t understand address sequence
Transfer cross over target’s address boundary
Burst memory transfer crosses cache line boundary
Retry ( if the target cannot permit any data to be transferred )
Reasons
Target very slow to complete first data phase ( Greater than 16 PCI clocks )
Snoop hit on modified cache line
Resource busy
Memory target locked
Target Abort ( if the target detects fatal error )
Reasons
Broken Target
I/O addressing error
Address phase parity error
Master abort on other side of PCI-to-PCI bridge
Type A Disconnect Type B Disconnect
Know in advance that the next data transfer takes more than 8 PCI clock
1 2 3 4 1 2 3 4
CLK CLK
FRAME# FRAME#
IRDY# IRDY#
TRDY# TRDY#
STOP# STOP#
DEVSEL# DEVSEL#
Data Data
Transfer Transfer
TRDY# asserted, STOP# asserted, TRDY# asserted, STOP# asserted,
DEVSEL# asserted, IRDY# deasserted DEVSEL# asserted, IRDY# asserted
Type C Disconnect Type C Disconnect
with IRDY# Asserted without IRDY# Asserted
Current data transfer takes more than 8 PCI clock
1 2 3 4 1 2 3 4
CLK CLK
FRAME# FRAME#
IRDY# IRDY#
TRDY# TRDY#
STOP# STOP#
DEVSEL# DEVSEL#
Data TRDY# deasserted, STOP# asserted Data
Transfer Transfer
DEVSEL# asserted
Retry Received Retry Received
With IRDY# Asserted Without IRDY# Asserted
1 2 3 4 1 2 3 4
CLK CLK
FRAME# FRAME#
IRDY# IRDY#
TRDY# TRDY#
STOP# STOP#
DEVSEL# DEVSEL#
TRDY# deasserted, STOP# asserted
No Data No Data
Transfer DEVSEL# asserted Transfer
Occurs in the first data phase
Target Abort Example
1 2 3 4
CLK
FRAME#
Master’s response to target abort:
• Generates an interrupt to alert is related IRDY#
device to check its status.
TRDY#
• Generates SERR#
STOP#
DEVSEL#
TRDY# deasserted, STOP# asserted
DEVSEL# deasserted
Shared Resource Acquisition
Shared Resource Acquisition
• LOCK#
Usage : Perform read/modify/write of a memory
semaphore as an atomic series to avoid
Synchronization Problem.
Solutions:
Bus LOCK : Permissible but not preferred
Resource LOCK: Preferred
Starting an Exclusive Access
( Establishing LOCK#)
CLK 1 2 3 4 5
FRAME#
( Master -> Target )
LOCK#
( Master -> Target )
AD ADDRESS DATA
( Master Target )
IRDY#
( Master -> Target )
TRDY#
( Target -> Master )
DEVSEL#
( Target -> Master )
GNT#
( Arbiter -> Target )
LOCK# Mechanism Availability:
Do not assert REQ# if LOCK# is currently asserted.
If FRAME# and LOCK# are deasserted, assert its REQ#.
The master continue to monitor LOCK# while waiting for GNT#.
If LOCK# is sampled asserted, the master deasserted its REQ#.
When the master samples bus idle ( FRAME# & IRDY# deasserted)
and LOCK# deasserted, it has acquisition of the bus and of the
LOCK#.
Accessing a Locked Agent : Retry
1 2 3 4 5
CLK
FRAME#
LOCK# (driven low by master holding lock)
ADDRESS DATA
AD
IRDY#
TRDY#
STOP#
DEVSEL#
GNT# Retry
Continuing & Completing an Exclusive Access
1 2 3 4 5
CLK
FRAME#
Release
LOCK# Continue
ADDRESS DATA
AD
IRDY#
TRDY#
DEVSEL#
GNT#
Error Detection and Handling
When Parity Error occurs:
Configuration status register : DETECTED PARITY ERROR
Configuration command register: PARITY ERROR RESPONSE
Assert PERR#
Devices excluded from PERR# Requirement
Chipsets
Devices that don’t deal with OS/Application program or data
Parity on Read Transaction
1 2 3 4 5 6 7 8 9
CLK
FRAME#
AD Address 1st 2nd 3rd Data
Data Data
BUS 1st Byte 2nd Byte 3rd Byte
C/BE# Enables Enables Enables
CMD
Add phase 1st Data 2nd Data
PAR parity parity parity 3rd Data Parity
3rd phase PERR#
earliest latest
PERR# 1st phase 2nd phase
PERR# PERR#
IRDY#
TRDY#
DEVSEL#
Parity on Write Transaction
1 2 3 4 5 6 7 8 9
CLK
FRAME#
AD Address 1st 2nd 3rd Data
Data Data
BUS 1st Byte 2nd Byte
C/BE# Enables Enables 3rd Byte Enables
CMD
Add phase 1st Data 2nd Data
PAR parity parity parity 3rd Data Parity
3rd phase PERR#
earliest latest
PERR# 1st phase 2nd phase
PERR# PERR#
IRDY#
TRDY#
DEVSEL#
Configuration Related Issues
Configuration Address Space Format
Byte Number
3 2 1 0
00
Configuration
Header Space
15
Double Word Number
16
Device Specific
Configuration
Registers
63
Configuration Registers
Type 0 Configuration Space Header
31 16 15 0
Required Device ID Vendor ID 00h
configuration Command
Status 04h
registers
Class Code Revision ID 08h
Header Type Latency Cache Line
BIST 0Ch
Timer Size
10h
Base Address Registers
24h
Cardbus CIS Pointer 28h
Subsystem ID Subsystem Vendor ID 2Ch
Expansion ROM Base Address 30h
Reserved 34h
Reserved 38h
Max_Lat Min_Gnt Interrupt Pin Interrupt Line 3Ch
Command Register Bit Assignment
15 10 9 8 7 6 5 4 3 2 1 0
Reserved
Fast Back-to-Back Enable
SERR# Enable
Wait Cycle Control
Parity Error Response
Palette Snoop Enable
Memory Write and Invalidate Enable
Special Cycle Monitoring
Enable Mastering
Memory Access Enable
I/O Access Enable
Status Register
15 14 13 12 11 10 9 8 7 6 5 4 0
Reserved
66MHz-Capable
UDF Supported
Fast Back-to-Back Enable
Data Parity Reported
DEVSEL Timing
Signaled Target Abort
Received Target Abort
Received Master Abort
Signaled System Error
Detected Parity Error
Class Code Register
23 16 15 8 7 o
Class Code Sub-Class Code Prog I/F
Basic function More specific Device specific
device subclass programming
interface
Eg. 06h 01h 00h
Bridge device PCI/ISA bridge
Header Type Register
7 6 0
Header Type
Configuration Header Format
0 = single function device
1 = multi function device
BIST Register
7 6 5 4 3 0
Reserved Completion Code
Start BIST
BIST Capable
Memory Base Address Register
31 4 3 2 1 0
Base Address 0
Prefetchable
Type
Memory space
indicator
Bits 2-1
00 Base register is 32 bits wide and can be mapped anywhere in the 32-bit memory space.
01 Base register is 32 bits wide must be mapped below 1M in memory space.
10 Base register is 64 bits wide and can be mapped anywhere in the 64-bit memory space.
11 Reserved
Bit 3 : set 1 if prefetchable, set 0 otherwise
I/O Base Address Register
31 2 1 0
Base Address 1
Reserved
I/O space
indicator
Expansion ROM Register
31 11 10 1 0
Expansion ROM Base Address (Upper 21 bits) Reserved
Address decode enable
Configuration Transactions
• Usage: Access PCI configuration registers
A PCI device or host/PCI bridge require 64 doubleword of config. register
Each PCI function requires 64 doubleword of config. register
• Transaction type:
1. Type 0 configuration read or write transaction
2. Type 1 configuration read or write transaction
3. Memory mapped configuration mechanism ( PowerPC )
• Configuration mechanism:
1. Mechanism 1 ( Preferred)
2. Mechanism 2
Peer Host/PCI Bridges System
Memory
Processor
Memory
controller
Host Bus
Bridge A Bridge B
PCI Bus 0 PCI Bus 4
Expansion
Bridge Bridge D PCI Device Bridge E PCI Device Bridge C
PCI Bus 0
PCI Bus 0
Expansion bus PCI bus 1 PCI bus 3 PCI bus5
Bridge C
PCI bus 2
Type 0 Configuration Transaction
• Two 32 bit I/O ports are utilized at I/O address:
CONFIG_ADDRESS PORT: 0CF8 h - 0CFB h
CONFIG_DATA PORT : 0CFC h - 0CFF h
• Configuration Address Register at 0CF8h
31 30 24 23 16 15 11 10 8 7 2 1 0
Bus Device Function DW
Reserved 0 0
1 = Enable
Number Number Number Number
Configuration
space mapping 0CFBh 0CFAh 0CF9h 0CF8h
• Contents of the AD bus during address phase
31 30 11 10 8 7 2 1 0
Function DW
Reserved 0 0
Number Number
0CFBh 0CFAh 0CF9h 0CF8h
Implementation of IDSEL
31 30 24 23 16 15 11 10 8 7 2 1 0
Bus Device Function DW
Reserved 0 0
Number Number Number Number
Decoder
Device Number
16 15 14 ………. 1 0
31 30 …….. 16 15 11 10 8 7 2 1 0
…….. Function DW
0 0
Number Number
IDSEL IDSEL IDSEL IDSEL
....
PCI Slot 4 PCI Slot 3 PCI Slot 2 PCI Slot 1
Type 0 Configuration Read Access
1 2 3 4 5 6 7 8 9
CLK
FRAME#
AD Address Data
C/BE# Config Read Byte Enables
CMD
IRDY#
TRDY#
IDSEL#
GNT#
Configuration START
Mechanism 1
Processor write to Pass PCI-to-PCI bridge
config. address reg.
at I/O port 0CF8
Target bus in the range
Host/PCI bridge
Bus num the YES
YES
Bus num the same
same
NO
NO Type 0 configuration
Type 0 configuration read read or write at config.
or write at config. data data port 0CFC
port 0CFC
Type 1 config.
Type 1 config. transaction
transaction
Interrupt Related Issues
• Value to be Hardwired into Interrupt Pin Register
Interrupt Signal Bonded To Value Hardwired In Pin Register
Device doesn’t generate interrupts 00h
INTA# pin 01h
INTB# pin 02h
INTC# pin 03h
INTD# pin 04h
• Interrupt Line Register Values
System IRQ Line Interrupt Routed to Value to be Written In Line Register
IRQ0 0d
IRQ1 1d
IRQ2 2d
IRQ15 15d
Interrupt Design
Programmable
INTA#
Interrupt router
INTA#
INTB#
Slave
INTA# 8259
INTA#
INTB#
INTC#
IRQ8-15
INTA#
INTB# INTD#
INTC#
INTD#
INTA# Master
8259
INTA#
INTB# IRQ0-7
INTA#
Interrupt Chaining
Device 8259
IRQ 1 Entry 1 ISR 1
INT A
INT B IRQ 2 Entry 2 ISR 2
If INT A and INT B both routed to IRQ1:
ISR 2 with
INT B IRQ 1 Entry 2 Entry 1
embedded
PCI Cache Support
• Snoop
SDONE : snoop done
SBO# : snoop backoff. ( HITM when assert.)
• The non-cacheable transaction is regardless of SDONE and SBO#.
• Write Through : only use SDONE
• Memory Target Interpretation of Snoop Result Signal from Bridge
SDONE SBO# Description
0 X Standby
1 1 Clean snoop
1 0 Hit on a modified line
Wait States Inserted Until Snoop Completes
CLK
1 2 3 4 5 6
FRAME#
ADDRESS DATA
AD
IRDY#
TRDY#
SDONE
SBO#
Hit to a Modified Line Followed by the Writeback
CLK
1 2 3 4 5 6 A B C
FRAME#
writeback transaction
ADDRESS DATA-1 ADDRESS DATA-1 DATA-2
AD
IRDY#
TRDY#
DEVSEL#
STOP#
SDONE
SBO#
STANDBY HITM HITM HITM HITM CLEAN STANDBY
Expansion ROMs
Purpose:
device-specific power-on self-test code
device-specific initialization code
device-specific interrupt routine
device-specific BIOS routine
device-specific code to be executed during the system boot process
ROM Detection:
Check if Expansion yes Read if the first two yes
ROM base address locations on base address ROM exist
register exist register contain 55AAh
Code image copied to system DRAM
Execute initialization code
Code Image Format Header
Data structure Runtime Module
within the Image
Runtime Code
Initialization Code
(Can be discarded
after execution)
Checksum
Unused space
PCI Expansion ROM Header Format
Offset Length Value Description
0h 1h 55h ROM Signature,byte 1
1h 1h AAh ROM Signature,byte 2
2h-17h 16h XX Reserved(processor architecture unique data)
18h-19h 2h XX Pointer to PCI Data Structure
Unique Data Area in ROM Header
Offset Length Description
02h 1 Overall size of the image
03h-05h 3 Entry point for the initialization code
( POST performs a far call to initialize the device)
06h-17h 18 Reserved
PCI Data Structure Format
Offset Length Description
0h 4 Signature, the string “PCIR”
4h 2 Vendor Identification
6h 2 Device Identification
8h 2 Pointer to Vital Product Data
Ah 2 PCI Data Structure Length
Ch 1 PCI Data Structure Revision
Dh 3 Class Code
10h 2 Image Length
12h 2 Revision Level of Code/Data
14h 1 Code Type
15h 1 Indicator (Bit 7, “1” last image)
16h 2 Reserved