IRCC datasheet(73/79 Pages) SMSC

73 / 79 page

Receive

Description

Receiving messages with Programmed I/O using

FIFO Interrupt requires reading a fixed number of

data bytes, usually related to the threshold,

whenever the FIFO Interrupt becomes active.

An appropriate FIFO Threshold value allows the

host to efficiently satisfy the FIFO service

requests

until

the

message

reception

complete.

Example: Receive a 256-byte IrDA Message

Set an appropriate FIFO Threshold for the

system type.

Set the FIFO Interrupt Enable active and

enable the receiver.

Service the FIFO Interrupts as required

(Figure 45).

Note: the amount of data

remaining in the FIFO following the last

service request (RxServReq) in Figure 45 is

probably less than the typical read block

size. This will occur when an IrDA EOF has

been detected, the FIFO Receive Threshold

has not been reached and the FIFO Not

Empty flag is true.

IOCHRDY Time-out

Description

In programmed I/O mode when AEN = low and

String Move = active, IOCHRDY can be used to

slightly extend the access cycle if the FIFO is

temporarily unable to fulfill the transfer request

(Figure 46). If IOCHRDY remains inactive for

more than 10us, a time-out error occurs and

subsequent IOCHRDY cycles are prevented until

the string move bit is specifically reactivated.

Because of the 10us IOCHRDY time-out, it is

recommended that string move timing only be

used for 1.152Mbps transfers and above.

DM A Enable

IOR

String M ove

Rx Enable

RxServReq

FIFO Int. Enable

FIFO Interrupt

EOM Interrupt

FIGURE 45 - INTERRUPT DRIVEN PROGRAMMED I/O RECEIVE TIMING

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