RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 188

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

6.0 Traffic Management
6.3 ABR Flow Control Manager
Figure 6-17. Cell Decision Table for Nrm = 32
6-28
FWD_INDEX
APPLICATION EXAMPLE: Cell Decision Table for Nrm=32
The Figure below, shows a typical Cell Decision Table. The anchor of the table, the FWD_INDEX
ACDB, is located at index 100 of the ABR Decision Table. Whenever a Forward RM cell is sent, this
ARCB will serve as the “reset” point for the decision state machine. When CELL_INDEX =
FWD_INDEX, a steady state ABR channel will transmit a Backward RM cell and advance the
CELL_INDEX. The diagram shows the next ACDB (101) in more detail. It contains the 16 Cell Type
Actions (BRM = Send Backward RM etc.). At the next cell transmission opportunity, the ABR Flow
Control Manager state machine will select a cell type by indexing into the ACDB according to the
ACDV . In this case, the only condition present is RUN=1, so ACDV = 0001b. Cell Type Action Index
1 is selected. For this ACDB, Cell Type Action 1 is DATA or “Send Data Cell”. Therefore, the RS8234
will transmit a user data cell.
transmits a Forward RM Cell under all circumstances. Therefore, the RS8234 resets the CELL_INDEX
for this VCC to FWD_INDEX = 100, when it reaches this ACDB.
Forward RM cell, and the sequence would continue from the FWD_INDEX.
In this example, the Host should initialize CELL_INDEX to 131. The RS8234 would transmit a
In steady state, CELL_INDEX will be incremented until it reaches ACDB 131. This ACDB
Nrm = 32
129
130
131
100
101
102
104
103
Mindspeed Technologies
CELL_INDEX(++)
[TRM_EXP, TA_PND, TA_XMIT, RUN] = 0001b
15-FRM
ABR Cell Type Decision Vector (ACDV)
7-BRM
ATM ServiceSAR Plus with xBR Traffic Management
ABR CELL DECISION BLOCK
14-FRM
6-BRM
™
1-DATA
9-FRM
28234-DSH-001-B
0-NONE
8-FRM
RS8234
100074_056