M3885 datasheet(33/103 Pages) RENESAS

33 / 103 page

3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

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

Universal asynchronous transmitter receiver (UART) serial I/O

mode 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.

Both the transmit and receive shift registers have a buffer, but the

two buffers assigned the same address. Since the shift register

cannot be written to or read from directly, transmit data is written

to the transmit buffer register, and receive data is read from the re-

ceive 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.

Fig. 28 Block diagram of UART mode

f(XIN)

1/4

PE FE

1/16

Data bus

Receive buffer register

Receive shift register

Receive buffer full flag (RBF)

Receive interrupt request (RI)

Baud rate generator

Frequency division ratio 1/(n+1)

ST/SP/PA generator

Transmit buffer register

Data bus

Transmit shift register

Transmit shift completion flag (TSC)

Transmit buffer empty flag (TBE)

Transmit interrupt request (TI)

ST detector

SP detector

UART control register

Character length selection bit

BRG count source selection bit

Transmit interrupt source selection bit

Serial I/O synchronous clock selection bit

Clock control circuit

Character length selection bit

7 bits

8 bits

Serial I/O control register

P46/SCLK

Serial I/O status register

P44/RXD

P45/TXD

(f(XCIN) in low-speed mode)

Address

001816

Address

001A16

Address 001B16

Address 001916

M3885 Datasheet(PDF) 33 Page - Renesas Technology Corp

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