PM6344 datasheet(209/256 Pages) PMC

209 / 256 page

STANDARD PRODUCT

PMC-Sierra, Inc.

PM6344 EQUAD

PMC-951013

ISSUE 5

QUADRUPLE E1 FRAMER

196

c) If FLG=1 and the link state was inactive, then set the link state to active,

discard the last data byte, and go to step 1.

ELSE

d) Save the last data byte read.

e) If EOM=1, then read the CRC and NVB[2:0] bits of the RFDL Status

f) If FE=0, then go to step 2, else go to step 1.

DMA-Controlled Mode

The RFDL can also be used with a DMA controller to process the frame data. In

the DMA controlled mode, the RDLINT[x] output of the RFDL is used as a DMA

request input to the DMA controller, and the RDLEOM[x] output is used as an

interrupt to the processor to allow handling of exceptions and as an indication of

when to process a frame. The RXDMASIG bit of the Datalink Options Register

should be set to logic 1.

The RDLINT[x] output of the RFDL is connected through a gate to the DMA

request input of the DMA controller to optionally inhibit the DMA request if the

RDLEOM[x] output is high. The DMA controller reads the data bytes from the

RFDL whenever the RDLINT[x] output is high. When the current byte read from

the Data Register is the last byte in a frame (due to an end-of-message or an

abort), or an overrun condition occurs, then the RDLEOM[x] output goes high.

The DMA controller is inhibited from reading any more bytes, and the processor

is interrupted. The processor can then halt the DMA controller, read the Status

data for the next frame. The RDLEOM[x] output can optionally be enabled to

generate a processor interrupt through the common INTB output via the

RDLEOME bit in the Datalink Options register, rather than tying the RDLEOM[x]

output directly to the microprocessor. This allows a central microprocessor

controlling the EQUAD operation to also respond to conditions affecting the DMA

servicing of RFDL. When using the INTB output, the central processor must poll

the Interrupt ID/Clock Monitor, and the Interrupt Source Registers to identify the

source of the interrupt before beginning any interrupt service routine.

PM6344 Datasheet(PDF) 209 Page - PMC-Sierra, Inc