Z8F021ASH020SC datasheet(130/276 Pages) ZILOG

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PS022815-0206

Infrared Encoder/Decoder

Z8 Encore! XP® 4K Series

Product Specification

111

Receiving IrDA Data

Data received from the infrared transceiver using the IR_RXD signal through the RXD pin

is decoded by the Infrared Endec and passed to the UART. The UART’s baud rate clock is

used by the Infrared Endec to generate the demodulated signal (RXD) that drives the

UART. Each UART/Infrared data bit is 16-clocks wide. Figure 18 illustrates data recep-

tion. When the Infrared Endec is enabled, the UART’s RXD signal is internal to the Z8

Encore! XP® 4K Series products while the IR_RXD signal is received through the RXD

pin.

Figure 18.IrDA Data Reception

Infrared Data Reception

The system clock frequency must be at least 1.0 MHz to ensure proper reception of the

1.4

μs minimum width pulses allowed by the IrDA standard.

Endec Receiver Synchronization

The IrDA receiver uses a local baud rate clock counter (0 to 15 clock periods) to generate

an input stream for the UART and to create a sampling window for detection of incoming

pulses. The generated UART input (UART RXD) is delayed by 8 baud rate clock periods

with respect to the incoming IrDA data stream. When a falling edge in the input data

stream is detected, the Endec counter is reset. When the count reaches a value of 8, the

UART RXD value is updated to reflect the value of the decoded data. When the count

reaches 12 baud clock periods, the sampling window for the next incoming pulse opens.

The window remains open until the count again reaches 8 (in other words, 24 baud clock

periods since the previous pulse was detected), giving the Endec a sampling window of

Baud Rate

UART’s

IR_RXD

16 clock

period

Start Bit = 0

Data Bit 0 = 1

Data Bit 1 = 0

Data Bit 2 = 1

Data Bit 3 = 1

8 clock

delay

Clock

RXD

16 clock

period

16 clock

period

16 clock

period

16 clock

period

Start Bit = 0

Data Bit 0 = 1

Data Bit 1 = 0

Data Bit 2 = 1

Data Bit 3 = 1

min. 1.4

μs

pulse

Caution:

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