IRCC datasheet(72/79 Pages) SMSC

72 / 79 page

FIFO Interrupt Interface

Transmit

Description

Transmitting messages with Programmed I/O

using FIFO Interrupt requires writing 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 satsify the FIFO

service requests until the message transmission

is complete. For slow systems, the FIFO can be

manually filled with transmit data before the

transmitter is enabled.

Note: the FIFO will

automatically

request

service

before

the

transmitter is activated if the FIFO Threshold is

greater than zero.

Example: Transmit a 256-byte IrDA Message

Set an appropriate FIFO Threshold for the

system type. For the greatest performance

advantage, pre-load the FIFO with transmit

data.

Set the FIFO Interrupt Enable active and

activate the transmitter.

Service the FIFO Interrupts as required. Set

the Data Done flag when all of the transmit

message data has been loaded (Figure 44).

DMA Enable

IOW

String Move

FIFO Data WRITE

Status READ

FIFO FULL

FIGURE 43 - PROGRAMMED I/O WRITE TIMING

DMA Enable

IOW

String Move

Tx Enable

TxServReq

FIFO Int. Enable

FIFO Interrupt

Data Done

EOM Interrupt

FIGURE 44 - INTERRUPT DRIVEN PROGRAMMED I/O TRANSMIT TIMING

IRCC Datasheet(PDF) 72 Page - SMSC Corporation

IRCC Datasheet(HTML) 72 Page - SMSC Corporation

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