3850 datasheet(32/101 Pages) RENESAS

32 / 101 page

Rev.3.01

2003.06.20

page 32 of 97

3850 Group (Spec.H/A)

SERIAL I/O

qSERIAL I/O1

Serial I/O1 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/O1 mode selection bit of the serial I/O1 control register (bit

6 of address 001A16) to “1”.

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.

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

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

1/4

F/F

P26/SCLK1

Serial I/O1 status register

Serial I/O1 control register

P27/SRDY1

P24/RXD

P25/TXD

XIN

Receive buffer register

Address 001816

Receive shift register

Receive buffer full flag (RBF)

Receive interrupt request (RI)

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

Clock control circuit

Falling-edge detector

Transmit buffer register

Data bus

Address 001816

Shift clock

Transmit shift completion flag (TSC)

Transmit buffer empty flag (TBE)

Transmit interrupt request (TI)

Transmit interrupt source selection bit

Address 001916

Data bus

Address 001A16

Transmit shift register

RBF = 1

TSC = 1

TBE = 0

TBE = 1

TSC = 0

Transfer shift clock

(1/2 to 1/2048 of the internal

clock, or an external clock)

Serial output TxD

Serial input RxD

Write pulse to receive/transmit

buffer register (address 001816)

Overrun error (OE)

detection

Notes 1: As the transmit interrupt (TI), 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/O1 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 “1” .

Receive enable signal SRDY1

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