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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
62
performance statistics on channels and not for initiating packet specific
responses such as retransmission.
Transmit Channel Descriptor Reference Table
The TMAC maintains a Transmit Channel Descriptor Reference (TCDR) table in
which is stored certain information relating to DMA activity on each channel
together with TD pointers which are used by the TMAC to sort packet chains
supplied by the host into per-channel linked lists (see below). The caching of
DMA-related information reduces the number of host bus accesses required to
process each data packet, while the sorting into per-channel linked lists
eliminates head of line blocking. Each channel is provided with two entries in the
TCDR table, one for high priority packets (Pri 1) and one for low priority packets
(Pri 0). The structure of the TCDR table is shown in Figure 13 below.
Figure 13 – Transmit Channel Descriptor Reference Table
M CE
Last TD Pointer
A
D
Current TD Pointer
Bytes to Tx
[1 0]
AbrtIOC
Host TD Pointer
[13 0]
DMA Current Address
[31 0]
NA
PiP
Reserved
M CE
Last TD Pointer
[13 0]
Bytes to Tx
[1 0]
A
D
Current TD Pointer
[13 0]
Host TD Pointer
[13 0]
AbrtIOC
DMA Current Address
[31 0]
NA
PiP
M CE
Last TD Pointer
A
D
Current TD Pointer
Bytes to Tx
[1 0]
AbrtIOC
Host TD Pointer
[13 0]
DMA Current Address
[31 0]
NA
PiP
:
:
:
Bit 31
Bit 0
TCC 0, Pri 0
TCC 1, Pri 0
TCC 31, Pri 1
Next TD Pointer
[13 0]
Reserved
Next TD Pointer
[13 0]
Reserved
Next TD Pointer
[13 0]
V
V
V
Last
M
U
Last
M
U
M
U