IRCC datasheet(60/79 Pages) SMSC

60 / 79 page

CRC Select Timing

During transmit if the CRC Select control is low

the FCS is assumed to be part of the message

payload data sent from the Host and the

hardware CRC generator is not engaged (Figure

28). During receive if the CRC Select control is

low the hardware CRC generator is not engaged,

no comparison with the received FCS is made,

and the state of the configuration register CRC

Error flag is undefined.

During transmit if the CRC Select control is high

the FCS is assumed not to be part of the

message data sent from the Host, the hardware

CRC generator is engaged, and the FCS result is

appended to the Host payload data (Figure 29).

During receive, if the CRC Select control is high,

the output from the hardware CRC generator is

compared to the CRC from the received

message and the result recorded in the

configuration register CRC Error flag. Note: for

all IrDA FIR received messages, the FCS is sent

to the Host through the FIFO regardless of the

state of the CRC Select control.

EOF

FCS

BOF

FIFO Empty

EOM

CRC Select

Data Done

FIGURE 28 - IrDA FIR FRAME WITH SOFTWARE CRC

CRC

(HW )

EOF

FCS

BOF

FIFO Empty

EOM

CRC SELECT

Data Done

FIGURE 29 - IrDA FIR FRAME WITH HARDWARE CRC

IRCC Fiches technique(PDF) 60 Page - SMSC Corporation