![](http://datasheet.mmic.net.cn/330000/PM7367-PI_datasheet_16444408/PM7367-PI_75.png)
DATA SHEET
PM7367 FREEDM-32P32
ISSUE 2
PMC-1991499
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE
61
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
00
Last or only buffer of packet, buffer read.
01
Buffer of partial packet, buffer read.
10
Unprovisioned channel, buffer not read.
11
Malformed packet (e.g. Bytes In Buffer field
set to 0), buffer not read.
Status[2]
Description
0
No underflow detected.
1
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