ST7538
Host Processor Interface
ST7538 exchanges data with the host processor thorough a serial interface.
The data transfer is managed by REG_DATA and
RxTx
Lines, while data are exchanged using RxD, TxD
and CLR/T lines.
Four are the ST7538 working modes:
s
Data Reception
s
s
s
Data Transmission
Control Register Read
Control Register Write
REG_DATA and
RxTx
lines are level sensitive inputs.
Table 4.
REG_DATA
Data Transmission
Data Reception
Control Register Read
Control Register Write
0
0
1
1
RxTx
0
1
1
0
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
Data Interface
RxD
TxD
RxTx
CLR/T
REG_DATA
Synchronous
Data Interface
RxD
TxD
RxTx
CLR/T
REG_DATA
Host Controller
ST7538
Host Controller
D03IN1415
ST7538
– Asynchronous Mode.
ST7538 allows to interface the Host Controller using a 3 line interface (RXD,TXD &
RxTx
).
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.
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STMICROELECTRONICS [ STMICROELECTRONICS ]
