M38268EBFS datasheet(30/91 Pages) RENESAS

30 / 91 page

Rev.1.00

Sep 06, 2006

page 30 of 88

REJ03B0181-0100

3826 Group (One Time PROM version)

SERIAL INTERFACE

Serial I/O1

Serial I/O1 can be used as either clock synchronous or asynchro-

nous (UART) serial I/O. A dedicated timer (baud rate generator) is

also provided for baud rate generation.

(1) Clock Synchronous Serial I/O Mode

Clock synchronous serial I/O mode is selected by setting the se-

rial I/O1 mode selection bit of the serial I/O1 control register to “1”.

For clock synchronous serial I/O mode, the transmitter and the re-

ceiver must use the same clock as an operation clock.

When an internal clock is selected as an operation clock, transmit

or receive is started by a write signal to the transmit buffer regis-

ter.

When an external clock is selected as an operation clock, serial I/

O1 becomes the state where transmit or receive can be performed

by a write signal to the transmit buffer register. Transmit and re-

ceive are started by input of an external clock.

Fig. 26 Block diagram of clock synchronous serial I/O1

Fig. 27 Operation of clock synchronous serial I/O1 function

P46/SCLK1

P47/SRDY1

P44/RXD

P45/TXD

XIN

1/4

F/F

Serial I/O1 status register

Serial I/O1 control register

Receive buffer register

Address 001816

Receive shift register

Receive buffer full flag (RBF)

Receive interrupt request

Receive clock control circuit

Shift clock

Serial I/O1 synchronous

clock selection bit

Frequency division ratio 1/(n+1)

Baud rate generator

Address 001C16

BRG count source selection bit

Falling-edge detector

Data bus

Address 001816

Shift clock

Transmit shift register shift completion flag (TSC)

Transmit buffer empty flag (TBE)

Transmit interrupt request

Transmit interrupt source selection bit

Address 001916

Data bus

Address 001A16

Transmit buffer register

Transmit shift register

Transmit clock control circuit

Receive enable signal SRDY1

RBF = “1”

TSC = “1”

TBE = “0”

TBE = “1”

TSC = “0”

Transmit and receive shift clock

(1/2 to 1/2048 of the internal

clock, or an external clock)

Serial output TXD

Serial input RXD

Write signal to receive/transmit

buffer register (address 001816)

Overrun error (OE)

detection

Notes 1 : After data transferring, the TxD pin keeps D7 output value.

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

be output continuously from the TXD pin.

3 : Select the serial I/O1 transmit interrupt request factor between when the transmit buffer register 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/O1 control register.

4 : The serial I/O1 receive interrupt request occurs when the receive buffer full flag (RBF) becomes “1”.

(Note 1)

(Note 3)

(Note 2)

(Note 3)

(Note 4)

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