Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
8.4.2 Transmit SC Control Block
Base address: 1200A0h (480280h byte)
Index: 2h
Number of entries: 16 (32 words)
Type: Read/Write
Long address = 1200A0 + 2 × service_class + offset
h
h
Byte address = 480280 + 8 × service_class + offset
h
h
Table 29. Transmit SC Control Block Summary
Byte
Offset
Long
Offset
Read or
Name
Write
Description
0h
0h
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.
4h
1h
TX_SC_STATE
R/W
SC state. This word controls the congestion state of
the set of same SCs. Initialize to 0.
8.4.2.1 TX_SC_CONFIG
Offset: 0h (0h byte)
Type: Read/Write
Format: Refer to the following table.
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 + 2TX_SC_EXP_MAX_QD
A value of 0h causes all cells for this SC to be dropped. A value of Fh 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 + 2TX_SC_EXP_CONG_QD
A value of 0h causes this SC to be in congestion at all times. A value of 1h may not be
used. A value of Fh 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.
163
PMC [ PMC-SIERRA, INC ]
