Information Technology Reference
In-Depth Information
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Class code and Revision - the class code defines PCI device type. It splits into two 8-bit
values with a further 8-bit value that defines the programming interface for the unit. The
first defines the unit classification (00h for no class code, 01h for mass storage, 02h for
network controllers, 03h for video controllers, 04h for multimedia units, 05h for memory
controller and 06h for a bridge), followed by a subcode which defines the actual type.
Typical codes are:
•
0100h - SCSI controller
0101h -
IDE controller.
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0102h - Floppy controller
0200h -
Ethernet network adapter
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0201h -
Token ring network adapter
0202h -
FDDI network adapter
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0280h -
Other network adapter
0300h -
VGA video adapter
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0301h -
XGA video adapter
0380h -
Other video adapter
•
0400h -
Video multimedia device
0401h -
Audio multimedia device
•
0480h -
Other multimedia device
0500h -
RAM memory controller
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0501h -
Flash memory controller 0580h
-
Other memory controller
•
0600h -
Host
0601h -
ISA Bridge
•
0602h -
EISA Bridge
0603h -
MAC Bridge
•
0604h -
PCI-PCI Bridge
0680h -
Other Bridge
31
0
Unit ID
Man. ID
Status
Command
Class code
Rev.
BIST
Header Latency
CLS
Base Address Register
64-byte
header
in PCI
configuration
space
Reserved
Reserved
Expansion ROM Base Address
Reserved
Reserved
MaxLat MinGNT
INT-Pin INT-Line
Figure 4.5
PCI configuration space
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BIST, header, latency, CLS - the BIST (built-in self test) is an 8-bit field, where the most
significant bit defines if the device can carry out a BIST, the next bit defines if a BIST is
to be performed (a 1 in this position indicates that it should be performed) and bits 3-0
define the status code after the BIST has been performed (a value of zero indicates no er-
ror). The header field defines the layout of the 48 bytes after the standard 16-byte header.
The most significant bit of the header field defines whether the device is a multifunction
device or not. A 1 defines a multi-function unit. The CLS (cache line size) field defines
the size of the cache in units of 32 bytes. Latency indicates the length of time for a PCI
