RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 178

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

6.0 Traffic Management
6.2 xBR Cell Scheduler Functional Description
6.2.6 xBR Tunnels (Pipes)
6-18
A CBR tunnel occupies schedule table slots in the same manner as a CBR VCC.
However, instead of serving one VCC, from one to four priority levels are served.
The VCCs within a CBR tunnel can be UBR, VBR (VBR1 or VBR2), and/or
ABR traffic. In the case of a UBR priority in a tunnel, the VCCs of the served
priority level are serviced in round-robin order. For any VBR/ABR priorities in a
tunnel, each VCC is shaped to its GCRA parameters within the CBR tunnel.
NOTE:
for that tunnel is reserved in the schedule table as schedule slots. The one-to-four
priority levels assigned to that tunnel are named at this time, and are written to the
PRI3, PRI2, PRI1, and PRI0 fields in the CBR_TUN_ID field for the schedule
slots reserved. PRI3 should specify the highest priority level for that tunnel, down
to PRI0 as the lowest assigned priority level for that tunnel. The scheduler
services the highest priority level that has data available on that priority queue at
each point a schedule slot for that tunnel becomes active. This serves as a
secondary shaping of the traffic assigned to these tunnel priorities. Any one
priority level can be assigned to only one CBR tunnel, and must not be assigned
as a priority to more than one tunnel. Additionally, all priority levels utilized
within a CBR tunnel need to be activated as a tunnel by setting the
TUN_ENA( × ) bit(s) in the SCH_PRI and SCH_PRI2 registers.
scheduling priority assigned. All can be VBR/ABR tunnels. On the other hand,
the system designer can establish four tunnels, each of which has four scheduling
priorities assigned to it, or any combination of tunnels, which includes up to a
total of 16 scheduling priorities. Individual VCCs are assigned to the tunnel by
the host, by setting the PRI field in the VCC table to the priority of the tunnel.
enter a priority level higher than priority 7 in PRI0, you should assign the
difference in values as an offset, in the TUN_PRI0_OFFSET field in the
SCH_CTRL register.
the highest priority level(s) to CBR tunnel(s).
When the user establishes a CBR tunnel, the user-defined transmit bandwidth
Sixteen tunnels can be active at once, if each of these tunnels has only one
The 3-bit PRI0 field allows the entry of only priority levels 0–7. If you wish to
If both non-tunnel and tunnel scheduling priorities exist, the host must assign
The format of a CBR tunnel schedule table slot is not backward-
compatible with the CBR tunnel format used in the Bt8233 SAR.
Mindspeed Technologies
ATM ServiceSAR Plus with xBR Traffic Management
™
28234-DSH-001-B
RS8234