PMC-Sierra, Inc.
PM73488 QSE
L
PMC-980616
Issue 3
5 Gbit/s ATMSwitch Fabric Element
Released
Datasheet
40
3.1.2
Data Cell Format
The regular cell format is shown in Table 5.
Table 5. Regular Cell Format
Nibble
Symbol
Definition
Comment
0
PRES(1:0),
MC,
SP
Pres = 10
b
: Cell present.
01
b
: Cell not present (See
Table 6 on page 41
).
00
b
: Cell assumed to be not present (failure).
11
b
: Cell assumed to be not present (failure).
MC = 1
b
: Multicast Cell.
SP
Spare bit.
The spare bit is not interpreted
or used by the QSE.
1
SP(1:0),
PRIORITY(1:0)
SP(1:0) Spare bits.
Priority = 11
b
: High-priority cell.
10
b
: Medium-priority cell.
01
b
: Low-priority cell.
00
b
: Undefined. Cell discarded by QSE.
Priority for the switching fabric.
The QRT should be configured
never to generate priority 00
b
cells, since they are discarded
by the QSE.
The spare bits are not
interpreted or used by the QSE.
2
TAG_0
Routing tag 0 or
MULTICAST_GROUP_INDEX(15:12). Refer to
section
9.3.3 “MULTICAST_GROUP_INDEX_REGISTER” on
page 96
.
3
TAG_1
Routing tag 1 or
MULTICAST_GROUP_INDEX(11:8). Refer to
section
9.3.3 “MULTICAST_GROUP_INDEX_REGISTER” on
page 96
.
4
TAG_2
Routing tag 2 or MULTICAST_GROUP_INDEX(7:4).
Refer to
section 9.3.3
“MULTICAST_GROUP_INDEX_REGISTER” on
page 96
.
Interpretation of TAG_5:0
depends on whether or not the
cell is a multicast cell.
5
TAG_3
Routing tag 3 or MULTICAST_GROUP_INDEX(3:0).
Refer to
section 9.3.3
“MULTICAST_GROUP_INDEX_REGISTER” on
page 96
.
6
TAG_4
Routing tag 4 or
MULTICAST_GROUP_INDEX(23:20).
Currently, QSE supports only
256K multicast group vectors,
i.e. it only uses multicast group
index(17:0). Therefore, bits
23:20 are ignored.
7
TAG_5
Routing tag 5 or
MULTICAST_GROUP_INDEX(19:16). Refer to
section
9.3.8 “MULTICAST_GROUP_INDEX_MSB” on
page 98
.
Currently, QSE supports only
256K multicast group vectors,
i.e. it only uses multicast group
index(17:0). Therefore, bits
(19:18) are ignored.
TAG_6
Routing tag 6.