RELEASED
PM7350 S/UNI DUPLEX
DATA SHEET
PMC-1980581
ISSUE 8
DUAL SERIAL LINK PHY MULTIPLEXER
3. Write the cell content to the Microprocessor Cell Data register. Cell data is
entered in the format illustrated in Fig. 11.
4. If the cell is not the last of the message, read and store the contents of the
Insert CRC-32 accumulator register. This step is not necessary if the next cell
to be inserted belongs to the same control channel as the current cell.
The above sequence is repeated as needed to insert more cells. The assertion of
the INSRDY bit of the Insert FIFO indicates that the FIFO is ready again to be
written to. Setting INSRST of the Insert FIFO Control register to logic 1 prior to
writing the last cell byte allows the overwriting of the cell data.
12.1.2 Reading Cell Data From a Control Channel
Reading cell data from a control channel is done by manipulating the
Microprocessor Extract FIFO Control and Microprocessor Extract FIFO Ready
registers. The following steps are required to read a cell from one of the Extract
FIFOs.
1. Poll the bit of EXTRDY[1:0] in the Microprocessor Extract FIFO Ready
registerhigh-speed. The EXTRDY[0] and EXTRDY[1] bits indicate the status
of the FIFO receiving control channel cells from the RXD1+/- and RXD2+/-
high-speed links, respectively. Alternately, service the interrupts that result
from setting the EXTRDYE bit in the Microprocessor Cell Buffer Interrupt
Control and Status register.
2. Select the Extract FIFO corresponding to the desired high-speed link by
writing its identification number to the EXTFSEL bit of the Microprocessor
Extract FIFO Control register. A logic 0 selects the RXD1+/- FIFO while a logic
1 selects the RXD2+/- FIFO.
3. Read the header of the cell to determine if it is the end of message and to
which virtual channel it belongs.
4. If CRC-32 protection is required, set the EXTCRCPR of the Microprocessor
Extract FIFO Control and Status register to logic 0 to enable the CRC-32
process. The Extract CRC-32 accumulation register can be preset for the first
cell of a message by writing a logic 1 to EXTCRCPR prior to enable the CRC-
32 calculation. If the cell is not the first one of a message and does not belong
to the same control channel as the previous cell read, initialize the Extract
CRC-32 Accumulator registers to the value saved from the previous cell read
for the control channel.
CRC-32 field check is done by setting the EXTCRCCHK bit of the
Microprocessor Extract FIFO Control register to logic 1. This causes the
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
185
PMC [ PMC-SIERRA, INC ]
