CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 189

• Manufacturer Part Number: CN8237EBGB
• Description: ATM SAR 622Mbps 3.3V ABR/CBR/GFR/UBR/VBR 456-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8237EBGB

• Package: 456BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 622 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.135 V

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
Figure 6-18. Backward_RM Flow Control, Block Diagram
28237-DSH-001-C
6.3.7.3 Backward RM
RSM/SEG
ABR Decision
Queue
Instruction Table
Cell Flow Control
ABR Exponent
Templates
ABR Rate
Table
Flow Control
The ABR Rate Decision table consists of many indexed entries. Each of these
entries is called an ABR Rate Decision Block or ARDB. Each ARDB represents a
possible transmission rate for an ABR VCC. The rate of an ARDB is a
monotonically increasing function of the index of the block.
storing its current ARDB index in the RATE_INDEX field of the SCH_STATE VCC
structure. This RATE_INDEX uniquely identifies the current transmission rate of the
VCC.
algorithm adjusts the state of a connection by a relative rate (RR) algorithm, in
response to the CI and NI bits. The second algorithm allows the network to
explicitly request a transmission rate in the ER RM cell field. Each of these
algorithms produces a candidate rate. The Source must adjust its rate to be less
than or equal to the lesser of these two candidates.
parameters into rate index space. Since rate indexes are a monotonically
increasing function of rate, the CN8237 selects the candidate with the lowest rate
index.
This algorithm can adjust the rate relative to the current rate. The adjusted rate
relates to the current rate by a constant multiplicative decrease or additive
increase. Specifically, the adjusted rate increases by (RIF × PCR) or decreases by
(RDF × ACR). These values are pre-calculated and used to formulate a CN8237
ABR Rate Instruction table, avoiding real time math.
Manager
ABR
The CN8237 tracks the state of each ABR connection’s transmission rate by
Backward RM cells deliver stimulus for two flow control algorithms. The first
The CN8237 computes both rate candidates by first mapping all rate
For the RR algorithm, the conversion is embedded in the ARDBs themselves.
(RATE_INDEX)
Figure 6-18
SCH_STATE
Table Entry
(CI, NI, and ER Fields)
SEG VCC
Mindspeed Technologies
Scheduler
SAR
illustrates a block diagram of Backward RM flow control.
Cell
Rate
Decision
Coprocessor
Segmentation
Reassembly
Coprocessor
™
BACKWARD_RM
Cell Stream
ABR
UNI
6.3 ABR Flow Control Manager
Destination
Network +
6.0 Traffic Management
ATM
8237_073
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