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PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATMTraffic Management Device
Released
Datasheet
163
8.4.2
Transmit SC Control Block
Base address: 1200A0
h
(480280
h
byte)
Index: 2
h
Number of entries: 16 (32 words)
Type: Read/Write
Long address = 1200A0
h
+
2
h
×
service_class
+
offset
Byte address = 480280
h
+ 8
h
×
service_class
+
offset
8.4.2.1
TX_SC_CONFIG
Offset: 0
h
(0
h
byte)
Type: Read/Write
Format: Refer to the following table.
Table 29. Transmit SC Control Block Summary
Byte
Offset
Long
Offset
Name
Read or
Write
Description
0
h
0
h
TX_SC_CONFIG
R/W
SC configuration word. This word defines the config-
uration of a set of SCs that stretch across all the trans-
mit VOs. This field is not present in the receive
direction. Initialize to the proper value. This word
may be modified during cell flow.
4
h
1
h
TX_SC_STATE
R/W
SC state. This word controls the congestion state of
the set of same SCs. Initialize to 0.
Field (Bits)
Description
Not present
(31:16)
RAM is not present in these bit locations.
TX_EXP_MAX_SC_QD
(15:12)
Exponent of the maximum per-SC queue depth. Initialize to the proper setting. Limits
the TX_SC_CUR_QD to:
TX_SC_CUR_QD
≤
1 + 2
TX_SC_EXP_MAX_QD
A value of 0
h
causes all cells for this SC to be dropped. A value of F
h
limits this SC to
31744 cells.
TX_EXP_CONG_SC_QD
(11:8)
Exponent of the congested per-SC queue depth. Initialize to the proper setting. The con-
gestion state is entered when the threshold is exceeded, and the congestion state is
exited when the queue length drops below 50 percent of this threshold. Enables conges-
tion management when:
TX_SC_CUR_QD > 1 + 2
TX_SC_EXP_CONG_QD
A value of 0
h
causes this SC to be in congestion at all times. A value of 1
h
may not be
used. A value of F
h
causes this SC to enter congestion at a depth of 31744 cells.
Not used
(7:0)
Write with a 0 to maintain software compatibility with future versions.