M38027E8SP Datasheet, PDF (19/51 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3802 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Asynchronous serial I/O (UART) mode
Clock asynchronous serial I/O mode (UART) can be selected by
clearing the serial I/O mode selection bit of the serial I/O control
register to “0”.
Eight serial data transfer formats can be selected, and the transfer
formats used by a transmitter and receiver must be identical.
The transmit and receive shift registers each have a buffer, but the
two buffers have the same address in memory. Since the shift reg-
ister cannot be written to or read from directly, transmit data is
written to the transmit buffer, and receive data is read from the re-
ceive buffer.
The transmit buffer can also hold the next data to be transmitted,
and the receive buffer can hold a character while the next charac-
ter is being received.
P44/RXD
P46/SCLK1
f(XIN)
P45/TXD
Data bus
Address 001816
Serial I/O1 control register Address 001A16
OE
Receive buffer
Character length selection bit
STdetector
7 bits
8 bits
Receive shift register
Receive buffer full flag (RBF)
Receive interrupt request (RI)
1/16
PE FE SP detector
Clock control circuit
UART control register
Address 001B16
Serial I/O1 synchronous clock selection bit
BRG count source selection bit
1/4
Frequency division ratio 1/(n+1)
Baud rate generator
Address 001C16
ST/SP/PA generator
1/16
Transmit shift completion flag (TSC)
Transmit shift register
Transmit interrupt source selection bit
Transmit interrupt request (TI)
Character length selection bit
Transmit buffer
Address 001816
Transmit buffer empty flag (TBE)
Serial I/O1 status register Address 001916
Data bus
Fig. 12 Block diagram of UART serial I/O
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