ST72E121J4D0 查看數據表（PDF） - STMicroelectronics

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ST72E121J4D0

8-BIT MCU WITH 8 TO 16K OTP/EPROM, 384 TO 512 BYTES RAM, WDG, SCI, SPI AND 2 TIMERS

STMicroelectronics 

ST72E121 ST72T121

4.4 SERIAL COMMUNICATIONS INTERFACE (SCI)

4.4.1 Introduction

The Serial Communications Interface (SCI) offers

a flexible means of full-duplex data exchange with

external equipment requiring an industry standard

NRZ asynchronous serial data format. The SCI of-

fers a very wide range of baud rates using two

baud rate generator systems.

4.4.2 Main Features

s Full duplex, asynchronous communications

s NRZ standard format (Mark/Space)

s Dual baud rate generator systems

s Independently programmable transmit and

receive baud rates up to 250K baud.

s Programmable data word length (8 or 9 bits)

s Receive buffer full, Transmit buffer empty and

End of Transmission flags

s Two receiver wake-up modes:

– Address bit (MSB)

– Idle line

s Muting functionfor multiprocessor configurations

s Separate enable bits for Transmitter and

Receiver

s Three error detection flags:

– Overrun error

– Noise error

– Frame error

s Five interrupt sources with flags:

– Transmit data register empty

– Transmission complete

– Receive data register full

– Idle line received

– Overrun error detected

4.4.3 General Description

The interface is externally connected to another

device by two pins (see Figure 33):

– TDO: Transmit Data Output. When the transmit-

ter is disabled, the output pin returns to its I/O

port configuration. When the transmitter is ena-

bled and nothing is to be transmitted, the TDO

pin is at high level.

– RDI: Receive Data Input is the serial data input.

Oversampling techniques are used for data re-

covery by discriminating between valid incoming

data and noise.

Through this pins, serial data is transmitted and re-

ceived as frames comprising:

– An Idle Line prior to transmission or reception

– A start bit

– A data word (8 or 9 bits) least significant bit first

– A Stop bit indicating that the frame is complete.

This interface usestwo types of baud rate generator:

– A conventional type for commonly-used baud

rates,

– An extended type with a prescaler offering a very

wide range of baud rates even with non-standard

oscillator frequencies.

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