RELEASED
PM7350 S/UNI DUPLEX
DATA SHEET
PMC-1980581
ISSUE 8
DUAL SERIAL LINK PHY MULTIPLEXER
12
OPERATION
12.1 Microprocessor Inband Communication
In the upstream direction, the S/UNI-DUPLEX broadcasts control channel cells
on both the active and spare high-speed serial links. The contents of the cells
shall distinguish the two control channels if necessary. In the downstream
direction, each high-speed serial link has a dedicated queue for the control
channel cells.
The S/UNI-DUPLEX includes hardware support for CRC-32 generation and
verification. It consists of two accumulator registers, the Insert CRC-32
Accumulator register for control channel in the upstream direction and the Extract
CRC-32 Accumulator for control channel in the downstream direction. To allow
context change, each accumulator register can be preset, read and written by the
microprocessor.
12.1.1 Inserting Cells Into Control Channels
Cells are inserted into control channels by manipulating the Microprocessor
Insert FIFO Control and Microprocessor Insert FIFO Ready registers. The
following steps are required to insert a cell:
1. Poll the INSRDY bit in the Microprocessor Insert FIFO Ready. Alternately,
service the interrupts that result from setting the INSRDYE bit in the
Microprocessor Cell Buffer Interrupt Control and Status register.
2. If CRC-32 calculation is required set the INSCRCPR of the Microprocessor
Insert FIFO Control register to logic 0 to enable the CRC-32 process. The
Insert CRC-32 Accumulation register can be preset by writing a logic 1 to
INSCRCPR prior to enabling the CRC-32 calculation.
If the cell is not the first of the message, write the Insert CRC-32 Accumulator
register with the value stored at the end of the previous cell for the same
control channel. This step is not necessary if the last cell inserted belonged
to the same control channel as the current cell.
Insertion of the CRC-32 field is done by setting the INSCRCEND bit of the
Microprocessor Insert FIFO Control register to logic 1 prior to writing the last
cell of the CPCS-PDU. The S/UNI-DUPLEX will overwrite the data of the last
four bytes of the cell payload written by the microprocessor with the ones
complement of the content of the Insert CRC-32 Accumulator register.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
184
PMC [ PMC-SIERRA, INC ]
