CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 196

• 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

6.0 Traffic Management
6.3 ABR Flow Control Manager
6-40
6.3.7.7 Optional Rate
Adjustment Due to
Use-It-Or-Lose-It
Behavior
The use-it-or-lose-it behavior defined in TM 4.1 describes a rate adjustment for a
VCC that has a high ACR but is not actually using that bandwidth in
transmission. In this case, the ACR is lowered to the level of ICR for that channel.
the system designer to exactly tailor its operation. It uses a simple timeout
mechanism, dictatable for each explicit rate.
the ACR_ENA bit to a logic high in each of the corresponding ABR Rate
Decision Blocks. As a general guideline, this bit would only be set in those
ARDBs dictating rates above ICR.
two other values: ACR_TO (the trigger time for the timeout value when the rate
adjustment function activates), and ACR_INDEX (the new lower explicit rate
index to be established when the use-it-or-lose-it behavior is triggered).
Time Factor (ADTF), and ACR_INDEX should be patterned on the rate index for
ICR.
compares RM_TIME (the schedule slot count at the time the last Forward RM
cell was generated) with ACR_TO. If the trigger point for the timeout has been
reached, the CN8237 generates a new Forward RM cell with the ACR_INDEX
value as the assigned new explicit rate.
The CN8237’s implementation of the TM 4.1 use-it-or-lose-it behavior allows
The designer selectively enables this function for the chosen rate(s) by setting
In those ARDBs which have this function enabled, the designer also specifies
As a general guideline, ACR_TO should be patterned on the ACR Decrease
During run time on those ARDBs with the ACR_ENA bit set, the CN8237
Mindspeed Technologies
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
™
28237-DSH-001-C
CN8237