ST72T331 STMICROELECTRONICS [STMicroelectronics], ST72T331 Datasheet - Page 58

• Manufacturer Part Number: ST72T331
• Description: 8-BIT MCU WITH 8 TO 16K OTP/EPROM, 256 EEPROM, 384 TO 512 BYTES RAM, ADC, WDG, SCI, SPI AND 2 TIMERS
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72E331 ST72T331
5.5 SERIAL COMMUNICATIONS INTERFACE (SCI)
5.5.1 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.
5.5.2 Main Features
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Full duplex, asynchronous communications
NRZ standard format (Mark/Space)
Dual baud rate generator systems
Independently programmable transmit and
receive baud rates up to 250K baud.
Programmable data word length (8 or 9 bits)
Receive buffer full, Transmit buffer empty and
End of Transmission flags
Two receiver wake-up modes:
– Address bit (MSB)
– Idle line
Muting function for multiprocessor configurations
Separate enable bits for Transmitter and
Receiver
Three error detection flags:
– Overrun error
– Noise error
– Frame error
Five interrupt sources with flags:
– Transmit data register empty
– Transmission complete
– Receive data register full
– Idle line received
– Overrun error detected
5.5.3 General Description
The interface is externally connected to another
device by two pins (see Figure 2.):
– TDO: Transmit Data Output. When the transmit-
– RDI: Receive Data Input is the serial data input.
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 uses two types of baud rate generator:
– A conventional type for commonly-used baud
– An extended type with a prescaler offering a very
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.
Oversampling techniques are used for data re-
covery by discriminating between valid incoming
data and noise.
rates,
wide range of baud rates even with non-standard
oscillator frequencies.