28478-ERR-003-A Datasheet, PDF (1/3 Pages) M/A-COM Technology Solutions, Inc. – MUSYCC Non-Conformance

500391A
July 15, 2002
CN8478/74A/72A/71A—Rev. C.
Errata: MUSYCC Non-Conformance
Product Affected: MUSYCC CN8478/74A/72A/71A devices—Rev. C
Non-Conformance Information
This information specifies the known anomalies and non-conformance to stated information
for the MUSYCC CN8478/74A/72A/71A devices.
The revision C is designated by Revision ID = 0Ch in CN8478 PCI Configuration Space—
Function 0 and Function 1.
1. Jump Service Request
Description:
MUSYCC cannot process a jump service request from a host-owned, no-poll message
descriptor. What is meant by the word “from” is as follows. During message descriptor
processing, if MUSYCC encounters a host-owned descriptor, MUSYCC stops processing that
message descriptor and proceeds to check other groups for a message descriptor that it has
permission to process. If polling is set, MUSYCC returns to that same message descriptor to
see if it has permission to process that message descriptor. The message descriptor where
MUSYCC stops, due to host ownership, is the “from” message descriptor. This message
descriptor is a sentinel, or a placeholder, to which MUSYCC must always return. If polling is
disabled—by setting the No Poll (NP) bit to 1 in the message descriptor—MUSYCC will not
check that message descriptor again until the host requests it to do so through a jump service
request. When a jump service request is issued, MUSYCC is supposed to jump to the message
descriptor that is pointed by the transmit head pointer. However, MUSYCC first returns to the
“from” message descriptor to confirm buffer ownership. If the “from” buffer is MUSYCC-
owned, then MUSYCC returns to process the transmit head pointer, and the subsequent
message descriptors, correctly completing the jump service request. If the “from” buffer
remains host-owned when MUSYCC returns to it after a jump service request, then correct
completion of the jump service request only occurs for the first few jump service requests after
device initialization. After about three jump service requests (which remain pointing to host-
owned buffers), MUSYCC stops responding to subsequent jump service requests and that
channel must be reactivated to continue normal channel processing. During this failure
condition, MUSYCC starts to poll the sentinel message descriptor (for the specific channel that
requested jump service), even if the message descriptor is configured for No Poll (NP bit = 1).
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