M3885 datasheet(32/103 Pages) RENESAS

32 / 103 page

3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

SERIAL I/O

Serial I/O

Serial I/O works as either clock synchronous serial I/O mode or

universal asynchronous receiver transmitter (UART) serial I/O

mode. A dedicated timer is also provided for baud rate generation.

(1) Clock Synchronous Serial I/O Mode

Clock synchronous serial I/O mode can be selected by setting the

serial I/O mode selection bit of the serial I/O control register (bit 6

of SIOCON) to “1”.

For clock synchronous serial I/O, the transmitter and the receiver

must use the same clock. When an internal clock is used, the

transfer starts by writing to the TB.

Fig. 26 Block diagram of clock synchronous serial I/O

Fig. 27 Operation of clock synchronous serial I/O function

1/4

F/F

P46/SCLK

Serial I/O status register

Serial I/O control register

P47/SRDY/CLKRUN

P44/RXD

P45/TXD

f(XIN)

Receive buffer register

Receive shift register

Receive buffer full flag (RBF)

Receive interrupt request (RI)

Clock control circuit

Shift clock

Serial I/O synchronous

clock selection bit

Baud rate generator

BRG count source selection bit

Clock control circuit

Falling-edge detector

Transmit buffer register

Data bus

Shift clock

Transmit shift completion flag (TSC)

Transmit buffer empty flag (TBE)

Transmit interrupt request (TI)

Transmit interrupt source selection bit

Data bus

Transmit shift register

(f(XCIN) in low-speed

mode)

Frequency division ratio 1/(n+1)

Address 001816

Address 001A16

Address 001C16

Address 001816

RBF = 1

TSC = 1

TBE = 0

TSC = 1

TBE = 1

TSC = 0

Transfer shift clock

(1/2 to 1/2048 of the internal

clock, or an external clock)

TxD pin

RxD pin

Write pulse to transmit buffer

Overrun error (OE)

detection

Notes 1: As the transmit interrupt (TI), which can be selected, either when the transmit buffer has emptied (TBE=1) or after the

transmit shift operation has ended (TSC=1), by setting the transmit interrupt source selection bit (TIC) of the serial I/O

control register.

2: If data is written to the transmit buffer register when TSC=0, the transmit clock is generated continuously and the next

serial data is output continuously from the TxD pin.

3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes “1” .

SRDY pin

M3885 Datasheet(PDF) 32 Page - Renesas Technology Corp

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