cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 209

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

CN8236
ATM ServiceSAR Plus with xBR Traffic Management
6.3.8 Boundary Conditions and Out-of-Rate RM Cells
28236-DSH-001-B
6.3.8.1 Calculated Rate
6.3.8.2 Out-of-Rate
6.3.8.3 Out-of-Rate
Backward RM Cells
Forward RM Cell
Boundaries
Generation
When the system designer pre-calculates the rates for the ARDB tables, those
rates must fall within the two obvious upper and lower rate boundaries—the lower
rate boundary should not fall below MCR, and the upper rate boundary should not
be calculated above PCR.
A mechanism must exist to restart scheduling of a VCC once the rate on that
channel has dropped to 0, or is below the schedule table minimum rate (that is, the
rate is less than one schedule slot on the schedule table). Out-of-rate Forward RM
cell generation provides this mechanism.
SCH_ABRBASE(OOR_ENA) to a logic high.
Rate Decision Block (ARDB). This enables out-of-rate Forward RM cell
generation for that rate.
scheduling of the VCC has halted, and SET_OOR at that rate = 1, the CN8236
sets the SCH_OOR bit in the VCC’s SCH_STATE to a logic high. The CN8236
then generates an out-of-rate Forward RM cell on that channel.
cells as follows:
The system designer can set the TA_OOR bit to a logic high in any ABR Rate
Decision Block. This enables the CN8236 sending a Backward RM cell
out-of-rate when there is a pending Turnaround RM cell scheduled at that rate but
not yet sent, and another Forward RM cell is received.
To globally enable out-of-rate Forward RM cell generation, set
The system designer can set the SET_OOR bit to a logic high in any ABR
When the actual cell rate on a channel has lowered to the point where
The CN8236 calculates the rate for generation of out-of-rate Forward RM
R
Mindspeed Technologies
=
=
R (OOR_INT
(maximum scheduled rate)
+
1) (VCC_MAX 2
=
sysclk SLOT_PER generated rate
™
+
1)
6.3 ABR Flow Control Manager
6.0 Traffic Management
6-41