CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 169

• 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
6.2.3 CBR Traffic
28237-DSH-001-C
APPLICATION EXAMPLE: Determining Maximum Rate
To achieve the maximum rate, the user assigns one VCC to every cell slot in the Schedule table.
This prevents any other VCC from being scheduled since this channel uses all of the available
slots.
6.2.3.1 CBR Rate
frequency(SYSCLK) = 66 MHz
SLOT_PER
Maximum Rate
Selection
R
max
= 1.4128 M cells/second
The CBR service category guarantees end-to-end bandwidth through the network.
Certain data sources, such as voice circuits and constrained Cell Delay Variation
(CDV), require this guarantee. CDV is a measure of the burstiness of traffic. The
ATM network supplies a minimum CDV for CBR channels by reserving cell
transmission opportunities for the connections.
table to a CBR VCC. This connection always sends a single cell during its
assigned slots. The system clock serves as a time reference for CBR cell
generation. The system’s designer programs the duration of schedule slots in
clock cycles in the SLOT_PER (slot period) field of the SCH_SIZE register.
For each CBR assigned cell slot, the CN8237 generates one cell on the specified
VCC. The maximum or base rate of CBR channels is determined by the duration
of a cell slot according to the equation below, where R
cells per second.
transmit a full cell, and its minimum bound should be no less than 40.
= 47 clocks/slot
The CN8237 generates CBR traffic by assigning specific slots in the Schedule
SLOT_PER must be nominally set to the number of clock cycles needed to
SLOT_PER =
Mindspeed Technologies
clock frequency (SYSCLK or SCHREF)
R
max
™
6.2 xBR Cell Scheduler Functional Description
max
is the maximum rate in
6.0 Traffic Management
6-13