Thermal/Mechanical Specifications and Design Guide 83
PECI Interface
PCI configuration reads may be issued in byte, word or dword granularities.
7.1.4.10.1 Command Format
The RdPCIConfig() format is as follows:
Write Length: 0x06
Read Length: 0x05 (dword)
Command: 0x61
Description: Returns the data maintained in the PCI configuration space at the
requested PCI configuration address. The Read Length dictates the desired data return
size. This command supports only dword responses with a completion code on the
processor PECI clients. All command responses are prepended with a completion code
that includes additional pass/fail status information. Refer to Section 7.1.7.2 for details
regarding completion codes.
Note that the 4-byte PCI configuration address and read data field defined in
Figure 7-40 are sent in standard PECI ordering with LSB first and MSB last.
7.1.4.10.2 Supported Responses
The typical client response is a passing FCS, a passing Completion Code and valid data.
Under some conditions, the client’s response will indicate a failure.
The PECI client response can also vary depending on the address and data. It will
respond with a passing completion code if it successfully submits the request to the
appropriate location and gets a response. Exactly what the receiving agent does with
the data or how it responds is up to that agent and is outside the scope of PECI 3.0.
Figure 7-40. RdPCIConfig()
Byte
Definition
0
Client Address
1
Write Length
0x06
2
Read Length
{0x02,0x03,0x05}
8
FCS
3
Cmd Code
0x61
10
Completion
Code
11
13
FCS
45 76
LSB MSBPCI Configuration Address
Host ID[7:1] &
Retry[0]
9
LSB Data (1, 2 or 4 bytes) MSB
12
14 15
Byte #
Table 7-13. RdPCIConfig() Response Definition (Sheet 1 of 2)
Response Meaning
Bad FCS Electrical error
Abort FCS Invalid command formatting (mismatched RL/WL/Command Code)
CC: 0x40 Command passed, data is valid.