IRCC2.0 datasheet(79/87 Pages) SMSC

79 / 87 page

Receive

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 47).

Note: The amount of data

remaining in the FIFO following the last

service request (RxServReq) in Figure 47 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

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

48).

IOCHRDY

remains

inactive for more than 10Fs, a time-out error

occurs and subsequent IOCHRDY cycles are

prevented until the string move bit is specifically

reactivated.

Because of the 10Fs IOCHRDY

time-out, it is recommended that string move

timing only be used for 1.152 Mbps transfers and

above.

DMA Enable

IOR

String Move

Rx Enable

RxServReq

FIFO Int. Enable

FIFO Interrupt

EOM Interrupt

FIGURE 47 - INTERRUPT DRIVEN PROGRAMMED I/O RECEIVE TIMING

IRCC2.0 Datasheet(PDF) 79 Page - SMSC Corporation

IRCC2.0 Datasheet(HTML) 79 Page - SMSC Corporation

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