M38860E1A-XXXGP View Datasheet(PDF) -

MITSUBISHI MICROCOMPUTERS

3886 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

(2) Asynchronous Serial I/O (UART) Mode

Clock asynchronous serial I/O mode (UART) can be selected by

clearing the serial I/O1 mode selection bit of the serial I/O1 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 register, and receive data is read

from the receive buffer register.

The transmit buffer register can also hold the next data to be

transmitted, and the receive buffer register can hold a character

while the next character is being received.

Data bus

P44/RXD

P46/SCLK1/OBF10

Address 001816

Serial I/O1 control register Address 001A16

OE

Receive buffer register

Character length selection bit

ST detector 7 bits

Receive shift register

8 bits

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

f(XIN)

BRG count source selection bit

(f(XCIN) in low-speed mode)

1/4

Frequency division ratio 1/(n+1)

Baud rate generator

Address 001C16

ST/SP/PA generator

1/16

Transmit shift completion flag (TSC)

P45/TXD

Character length selection bit

Transmit shift register

Transmit interrupt source selection bit

Transmit interrupt request (TI)

Transmit buffer register

Address 001816

Transmit buffer empty flag (TBE)

Serial I/O1 status register Address 001916

Data bus

Fig. 23 Block diagram of UART serial I/O1

27

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