BT8222EPFF CONEXANT [Conexant Systems, Inc], BT8222EPFF Datasheet - Page 154

• Manufacturer Part Number: BT8222EPFF
• Description: ATM Transmitter/Receiver with UTOPIA Interface
• Manufacturer: CONEXANT [Conexant Systems, Inc]

Appendix A: Transmit FIFO Port Rates
A.2 Port Priority
A-2
A.2 Port Priority
The user can define a priority for each port. This priority can range from 0 to 3,
with 0 being the highest priority. A higher priority port will always preempt one
with a lower priority. This priority is programmable for each register in bits 3–2 of
the CELL_GEN_X register.
lowest priority, arbitration is on a “round-robin” basis. For example, if Port 0 is
carrying CBR signals it should be assigned the highest priority. Ports 1 and 2,
carrying less jitter-sensitive data, can be programmed to a lower priority. Port 0
will preempt Ports 1 and 2 when data is available. As long as both ports have data
available, Ports 1 and 2 will alternate transmission in slots where Port 0 is not
active.
may break down for multiple ports sharing a priority above a lower priority port.
If the CN8223 has been transmitting at priority 1, and a priority 0 port preempts
this transmission; that priority 0 port will not share the channel with other ports. It
will continue winning arbitration until it no longer has data available. At that
time, another priority 0 or lower priority channels will be allowed to transmit.
A.3 Summary
The CN8223’s transmit rate shaping is controlled via a user-assigned priority and
rate for each FIFO port. The CN8223 scheduling attempts to provide a fair
arbitration algorithm and to limit burst transmission by a single channel on the
line. A system designer should consider each data stream’s characteristics when
choosing the port, priority, and rate to assign.
The user can configure multiple ports to be the same priority. Within the
Only the lowest priority ports should share a priority. Round-robin scheduling
Conexant
ATM Transmitter/Receiver with UTOPIA Interface
CN8223
10046C