
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATMTraffic Management Device
Released
Datasheet
156
8.3.1
Receive Service Class (RX SC) Control Block
Base address: 110000
h
(440000
h
byte)
Index: 1
h
Number of entries: 64 (320 words)
Type: Read/Write
Address =110000
h
+
offset + service_class
Table 27. Receive Service Class (RX SC) Control Block Summary
8.3.1.1
RX_SC_CONFIG
Offset: 0
h
(0
h
byte)
Type: Read/Write
Format: Refer to the following table.
Byte
Offset
Long
Offset
Name
Read or Write
Description
0-FC
h
0-3F
h
RX_SC_CONFIG
R/W
The exponents of the maximum and congested queue
depths for this SC.
100-1FC
h
40-7F
h
RX_SC_STATE
R/W (init only)
The current queue depth for this SC.
200-2FC
h
80-BF
h
RX_SC_CUR_CHAN
R/W (init only)
The current channel being serviced for this SC.
300-3FC
h
C0-FF
h
RX_SC_PREV_CHAN
R/W (init only)
The previous channel serviced for this SC.
400-4FC
h
100-13F
h
RX_SC_CH_COUNT
R/W (init only)
The number of channels with cells currently queued.
Field (Bits)
Description
Not present
(31:16)
RAM is not present in these bit locations.
RX_SC_EXP_MAX_QD
(15:12)
Exponent of the maximum per-SCQ depth. Initialize to the proper setting. Limits the
RX_SC_CUR_QD to:
RX_SC_CUR_QD
≤
1 + 2
RX_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.
RX_SC_EXP_CONG_QD
(11:8)
Exponent of the congested per-SCQ depth. Initialize to the proper setting. The conges-
tion 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 congestion
management when:
RX_SC_CUR_QD > 1 + 2
RX_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
(7:3)
Write with a 0 to maintain software compatibility with future versions.
RX_SC_EXP_WEIGHT
(2:1)
Defines the weight of the SC in the queue service decision algorithm.
weight = 2
(RX_SC_EXP_WEIGHT
×
2)
This allows weights of 1, 4, 16, or 64.
Not used
(0)
Write with a 0 to maintain software compatibility with future versions.