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ST7538

Host Processor Interface

ST7538 exchanges data with the host processor thorough a serial interface.

and CLR/T lines.

Four are the ST7538 working modes:

s

Data Reception

s

Data Transmission

s

Control Register Read

s

Control Register Write

Table 4.

s

Mains Access

ST7538 features two type of communication interfaces:

- Asynchronous

- Synchronous

The selection can be done through the internal Control Register.

Figure 1.

– Asynchronous Mode.

Data are exchange without any auxiliary Clock reference in an Asynchronous mode without adding any

protocol bits. The host controller has to recover the clock reference in receiving Mode and control the Bit

time in transmission mode. RxD line is forced to a low logic level when no carrier is detected.

REG_DATA

RxTx

Data Transmission

0

0

Data Reception

0

1

Control Register Read

1

1

Control Register Write

1

0

RxD

CLR/T

REG_DATA

RxTx

ST7538

Host Controller

TxD

Asynchronous

Data Interface

RxD

CLR/T

REG_DATA

RxTx

ST7538

Host Controller

TxD

Synchronous

Data Interface

D03IN1415