cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 183

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
6.3.3 Source and Destination Behaviors
6.3.4 ABR VCC Parameters
6.3.5 ABR Templates
28237-DSH-001-C
ABR’s Source and Destination Behavior Definitions are listed in the ATM
Forum’s TM 4.1 Specification. Refer to this specification for these definitions.
The state of each VCC is stored individually in its SEG VCC table entry. The
ABR parameters are stored in the SCH_STATE portion of the segmentation VCC
table entry. Due to the large number of ABR parameters, the SCH_STATE of
ABR VCCs requires an additional location in the SEG VCC table.
The ABR Templates reside in SAR SEG-shared memory in a region referred to as
the ABR Instruction table. The ABR Instruction table contains one or more
templates. Individual VCCs are assigned to a single template. Each template
supports a group of VCCs. The key parameters contained in and controlled by the
ABR Templates are PCR, Initial Cell Rate (ICR), MCR, RIF, RDF, and Nrm.
the SCH_STATE portion of the SEG VCC table entry for each connection, thus
giving either per-template or per-connection control of MCR and ICR. This
choice is globally set using the ADV_ABR_TEMPL bit in the SEG_CTRL
register.
CN8237 as a complete microcoded state machine.
Rate Decision table, and an Exponent table.
the transmitted in-rate cell stream.
state includes several vectors to other states, corresponding to different rates.
When an event forces a rate decision, the CN8237 decides which vector to follow
based on network stimulus (CI/NI), ER decisions, or internal timer/counter
expirations (ADTF and CRM).
function. This function maps a TM 4.1 floating point rate representation (in
particular, the RM cell Explicit Rate field) to a Rate Decision table index. The
Exponent table is indexed by the Explicit Rate exponent. This mapping function
normalizes the ER field rate to the CI/NI state-based rate decision. Once
normalized, a rate can be chosen based on the minimum of the two rates.
The user can define MCR and ICR from the ABR Templates or from fields in
These ABR Templates are furnished by Mindspeed, and are downloaded to the
Three components constitute a complete template: a Cell Decision table, a
The CN8237 uses the Cell Decision table to select a cell type for insertion into
The Rate Decision table maps ABR cell stream rates to logical states. Each
The Exponent table contains parameters for a piece-wise linear mapping
Mindspeed Technologies
™
6.3 ABR Flow Control Manager
6.0 Traffic Management
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