UPSD3422 datasheet(111/293 Pages) STMICROELECTRONICS

111 / 293 page

uPSD34xx

IrDA interface

111/293

IrDA interface

uPSD34xx devices provide an internal IrDA interface that will allow the connection of the

UART1 serial interface directly to an external infrared transceiver device. The IrDA interface

does this by automatically shortening the pulses transmitted on UART1’s TxD1 pin, and

stretching the incoming pulses received on the RxD1 pin. Reference Figures 39 and 40.

When the IrDA interface is enabled, the output signal from UART1’s transmitter logic on pin

TxD1 is compliant with the IrDA Physical Layer Link Specification v1.4 (www.irda.org)

operating from 1.2k bps up to 115.2k bps. The pulses received on the RxD1 pin are

stretched by the IrDA interface to be recognized by UART1’s receiver logic, also adhering to

the IrDA specification up to 115.2k bps.

Note:

In Figure 40 a logic '0' in the serial data stream of a UART Frame corresponds to a logic high

pulse in an IR Frame. A logic '1' in a UART Frame corresponds to no pulse in an IR Frame.

Figure 39.

IrDA interface

Figure 40.

Pulse shaping by the IrDA interface

UART1

IrDA

Interface

TxD

RxD

uPSD34xx

IrDA

Transceiver

TxD1-IrDA

RxD1-IrDA

SIRClk

AI10437

Start

Bit

Stop

Bit

UART Frame

Data Bits

Bit Time

Pulse Width = 3/16 Bit Time

Start

Bit

Stop

Bit

UART Frame

IR Frame

Data Bits

AI10438

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