T8207 Datasheet, PDF (118/158 Pages) Agere Systems – ATM Interconnect

CelXpres T8207
ATM Interconnect
Advance Data Sheet
September 2001
14 Registers (continued)
Table 93. PPD Information 1 (PPDI1) (0206h)
Name
ppd_pnt12_sel[5:0]
Bit Pos. Type
5:0 RW
Reset
Description
X PPD Pointer 12 Select. The ppd_pnt12_sel[5:0] bit field selects
which bit of the cell header, the cell bus routing header, or the tan-
dem routing header is used as this offset bit.
ppd_en_sel[5:0]
Reserved
11:6 RW
15:12 RO
The PPD pointer select bits are used to create an offset into the
PPD state memory. The PPD state memory is used to keep track
of AAL5 virtual channels for partial packet discard. Up to 8192 vir-
tual channels may be supported with these select fields. The
ppd_pnt12_sel[5:0] bits select the most significant bit of the PPD
state memory offset, and the ppd_pnt0_sel[5:0] bits select the
least significant bit of the offset. A value of zero to 31 selects bits
in the cell header where zero is the CLP bit and 31 is the most
significant bit of the GFC/VPI field. A value of 32 to 47 selects bits
in the tandem routing header where 32 is the least significant bit
and 47 is the most significant bit. A value of 48 to 63 selects bits
in the cell bus routing header where 48 is the least significant bit
and 63 is the most significant bit. The value, “110000,” is a special
case and may be used to force the value of this bit to ‘0.’ If this bit
is forced to zero, the bit position in the resultant pointer is always
‘0’ and is not extracted from the received cell.
X PPD Enable Select. The ppd_en_sel[5:0] bit field selects which
bit of the cell header, the cell bus routing header, or the tandem
routing header is used as this enable bit. The PPD enable select
bits are used to identify the AAL5 virtual channel and to enable
PPD. A value of zero to 31 selects bits in the cell header where
zero is the CLP bit and 31 is the most significant bit of the GFC/
VPI field. A value of 32 to 47 selects bits in the tandem routing
header where 32 is the least significant bit and 47 is the most sig-
nificant bit. A value of 48 to 63 selects bits in the cell bus routing
header where 48 is the least significant bit and 63 is the most sig-
nificant bit. The value, “110000,” is a special case and may be
used to force the value of this bit to ‘0.’ If this selected bit in the
received cell is one, the partial packet discard feature is enabled.
0 Reserved.
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