PECI Interface
94 Thermal/Mechanical Specifications and Design Guide
Note: The codes explicitly defined in Tab l e 7 - 2 3 may be useful in PECI originator response
algorithms. Reserved or undefined codes may also be generated by a PECI client
device, and the originating agent must be capable of tolerating any code. The Pass/Fail
mask defined in Ta b l e 7 - 2 2 applies to all codes, and general response policies may be
based on this information. Refer to Section 7.1.8 for originator response policies and
recommendations.
7.1.8 Originator Responses
The simplest policy that an originator may employ in response to receipt of a failing
completion code is to retry the request. However, certain completion codes or FCS
responses are indicative of an error in command encoding and a retry will not result in
a different response from the client. Furthermore, the message originator must have a
response policy in the event of successive failure responses. Refer to Tabl e 7 -23 for
originator response guidelines.
Refer to the definition of each command in Section 7.1.2 for a specific definition of
possible command codes or FCS responses for a given command. The following
response policy definition is generic, and more advanced response policies may be
employed at the discretion of the originator developer.
Table 7-23. Device Specific Completion Code (CC) Definition
Completion
Code
Description
0x40 Command Passed
CC: 0x80
Response timeout. The processor was not able to generate the required response in a timely
fashion. Retry is appropriate.
CC: 0x81
Response timeout. The processor was not able to allocate resources for servicing this
command. Retry is appropriate.
CC: 0x82
The processor hardware resources required to service this command are in a low power
state. Retry may be appropriate after modification of PECI wake mode behavior if
appropriate.
CC: 0x83-8F Reserved
CC: 0x90 Unknown/Invalid Request
CC: 0x91
PECI control hardware, firmware or associated logic error. The processor is unable to process
the request.
CC: 0x92-9F Reserved
Table 7-24. Originator Response Guidelines
Response After 1 Attempt After 3 Attempts
Bad FCS Retry Fail with PECI client device error.
Abort FCS Retry
Fail with PECI client device error if command was not invalid or
malformed.
CC: 0x8x Retry
The PECI client has failed in its attempts to generate a response.
Notify application layer.
CC: 0x9x
Abandon any further
attempts and notify
application layer
n/a
None (all 0’s)
Force bus idle (drive
low) for 1mS and retry
Fail with PECI client device error. Client may not be alive or may be
otherwise unresponsive (for example, it could be in RESET).
CC: 0x4x Pass n/a
Good FCS Pass n/a
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