PM7367 datasheet(75/323 Pages) PMC

75 / 323 page

PM7367 FREEDM-32P32

DATA SHEET

PMC-1991499

ISSUE 2

FRAME ENGINE AND DATA LINK MANAGER

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE

Table 10 – Transmit Descriptor Reference

Bit 16

Bit 0

STATUS[2:0]

TDR[13:0]

Field

Description

Status[2:0]

The TMAC fills in the Status field to indicate to the host

the results of processing the TD. The encoding is:

Status[1:0]

Description

Last or only buffer of packet, buffer read.

Buffer of partial packet, buffer read.

Unprovisioned channel, buffer not read.

Malformed packet (e.g. Bytes In Buffer field

set to 0), buffer not read.

Status[2]

Description

No underflow detected.

Underflow detected.

TDR[13:0]

The TDR[13:0] field contains the offset of the TD

returned.

If a TDR is returned to the host with the status field set to “10” (unprovisioned

channel), the TDR may point to a binary tree of TDs and buffers (as indicated by

the CE and V bits in the TDs). It is the responsibility of the host to traverse the

tree to reclaim all the buffers. If a TDR is returned to the host with the status

field set to any other value, the TDR will only point to one TD and buffer

regardless of the values of V and CE in that TD.

The underflow status bit (Status[2]) is normally attached to the TDR belonging to

a packet experiencing underflow. For long packets spanning multiple buffers,

underflow is reported only once at the first available TDR of that channel. All

subsequent TDRs of that packet will be returned normally without the underflow

status. In rare cases, due to internal buffering by the FREEDM-32, a packet may

experience underflow at the very end of a packet, just as the TDR is being

returned to the TDR free queue. The underflow status will then be reported in

the first TDR of the immediate next packet of that channel. Because of the

uncertainty with the reporting of underflows between the current verse the

subsequent packet, the underflow status should only be used to gather

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