M37544 Datasheet, PDF(27/68 Page) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

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M37544 Datasheet, PDF (27/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

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7544 Group

Serial I/O

âSerial I/O

Serial I/O can be used as either clock synchronous or asynchro-

nous (UART) serial I/O. 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)

to â1â.

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

must use the same clock. If an internal clock is used, transfer is

started by a write signal to the TB/RB.

P10/RXD

P12/SCLK

XIN

P13/SRDY

P11/TXD

Data bus

Address 001816

Receive buffer register

Serial I/O control register

Address 001A16

Receive buffer full flag (RBF)

Receive shift register

Receive interrupt request (RI)

Shift clock

Clock control circuit

BRG count source selection bit

1/4

Serial I/O synchronous

clock selection bit

Frequency division ratio 1/(n+1)

Baud rate generator 1/4

Address 001C16

F/F

Falling-edge detector

Clock control circuit

Shift clock

Transmit shift completion flag (TSC)

Transmit shift register

Transmit interrupt source selection bit

Transmit interrupt request (TI)

Transmit buffer register

Address 001816

Data bus

Transmit buffer empty flag (TBE)

Serial I/O status register Address 001916

Fig. 28 Block diagram of clock synchronous serial I/O

Transfer shift clock

(1/2 to 1/2048 of the internal

clock, or an external clock)

Serial output TxD

Serial input RxD

Receive enable signal SRDY

Write pulse to receive/transmit

buffer register (address 001816)

TBE = 0

TBE = 1

TSC = 0

RBF = 1

TSC = 1

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 serial

data is output continuously from the TxD pin.

3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes â1â .

Fig. 29 Operation of clock synchronous serial I/O function

Rev.1.04 2004.06.08 page 27 of 66

REJ03B0012-0104Z

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