T8207 Datasheet, PDF (140/158 Pages) Agere Systems – ATM Interconnect

CelXpres T8207
ATM Interconnect
Advance Data Sheet
September 2001
14 Registers (continued)
14.3.4.3 PPD State Memory
Table 124. PPD Memory (PPDM) (1000h to 13FEh)
Name
word0
word1
word2
word3
word4
word5
word6
word7
.
.
.
word1F9
word1FA
word1FB
word 1FC
word1FD
word1FE
word1FF
Offset
00h
02h
04h
06h
08h
0Ah
0Ch
0Eh
.
.
.
3F2h
3F4h
3F6h
3F8h
3FAh
3FCh
3FEh
Type
RW
Reset
Description
X This memory space contains 8192 AAL5 virtual channel PPD bits. The
PPD pointer bits in the cell header, cell bus routing header, and tandem
routing header, which are selected by the PPD pointer select bits, point
to a single bit in this memory space. If the bit for a corresponding AAL5
virtual channel is ‘0,’ no cells are dropped. If the bit is ‘1,’ all remaining
cells in the packet, except the last cell, are dropped. A PPD bit becomes
set when a cell in an AAL5 virtual channel packet is dropped. The last
cell of a packet is identified by the least significant bit of the PTI field in
the cell header, which is set to ‘1.’ The most significant bit of the PTI field
is also checked to be ‘0’ (user data). The final cell of the packet is sent,
and the corresponding PPD bit is cleared. The most significant bit of
word0 corresponds to AAL5 virtual channel zero, and the least signifi-
cant bit of word1FF corresponds to AAL5 virtual channel 8191.
140
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