M38039G8HKP datasheet(43/92 Pages) RENESAS

43 / 92 page

Rev.1.10

Nov 14, 2005

Page 43 of 91

REJ03B0166-0110

3803 Group (Spec.H QzROM version)

PRELIMINARY

Notice: This is not a final specification.

Some parametric limits are subject to change.

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

Clock asynchronous serial I/O mode (UART) can be selected by

clearing the serial I/O1 mode selection bit (b6) of the serial I/O1

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.

The transmit and receive shift registers each have a buffer, but

the two buffers have the same address in a memory. 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 receive 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 34. Block diagram of UART serial I/O1

Fig 35. Operation of UART serial I/O1

f(XIN)

1/4

PE FE

1/16

Data bus

Receive buffer register 1

Address 001816

Receive shift register 1

Receive buffer full flag (RBF)

Receive interrupt request (RI)

Baud rate generator

Frequency division ratio 1/(n+1)

Address 001C16

ST/SP/PA generator

Transmit buffer register 1

Transmit shift register 1

Address 001816

Transmit shift

completion flag (TSC)

Transmit buffer empty flag (TBE)

Transmit interrupt request (TI)

Address 001916

ST detector

SP detector

UART1 control register

Address 001B16

Character length selection bit

Address 001A16

BRG count source selection bit

Transmit interrupt source selection bit

Serial I/O1 synchronous clock selection bit

Clock control circuit

Character length selection bit

7 bits

8 bits

Serial I/O1 status register

Serial I/O1 control register

P46/SCLK1

P44/RXD1

P45/TXD1

(f(XCIN) in low-speed mode)

TSC=0

TBE=1

RBF=0

TBE=0

RBF=1

TBE=1

TSC=1*

Transmit or

receive clock

Transmit buffer

write signal

Serial output

TXD1

Receive buffer

read signal

Serial input

RXD1

Generated at 2nd bit in 2-stop-bit mode

1 start bit

7 or 8 data bit

1 or 0 parity bit

1 or 2 stop bit (s)

Notes 1: Error flag detection occurs at the same time that the RBF flag becomes “1” (at 1st stop bit, during reception).

2: As the transmit interrupt (TI), when either the TBE or TSC flag becomes “1”, can be selected to occur depending on the setting of the transmit interrupt source

selection bit (TIC) of the serial I/O1 control register.

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

4: After data is written to the transmit buffer when TSC=1, 0.5 to 1.5 cycles of the data shift cycle are necessary until changing to TSC=0.

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