SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7532 Group

MITSUBISHI MICROCOMPUTERS

21

[Serial I/O1 control register] SIO1CON

The serial I/O1 control register consists of eight control bits for the

serial I/O1 function.

[UART control register] UARTCON

The UART control register consists of four control bits (bits 0 to 3)

which are valid when asynchronous serial I/O is selected and set the

data format of an data transfer. One bit in this register (bit 4) is al-

[UART status register] UARTSTS

The read-only UART status register consists of seven flags (bits 0 to

6) which indicate the operating status of the UART function and vari-

ous errors. This register functions as the UART status register

(UARTSTS) when selecting the UART.

The receive buffer full flag (bit 1) is cleared to “0” when the receive

buffer is read.

If there is an error, it is detected at the same time that data is trans-

ferred from the receive shift register to the receive buffer, and the

receive buffer full flag is set. A write to the UART status register clears

all the error flags OE, PE, FE, and SE (bit 3 to bit 6, respectively).

Writing “0” to the serial I/O1 mode selection bits MOD1 and MOD0

(bit 7 and 6 of the Serial I/O1 control register ) also clears all the

status flags, including the error flags.

reset, but if the transmit enable bit (bit 4) of the serial I/O1 control

register has been set to “1”, the continuous transmit valid bit (bit 2)

becomes “1”.

[Transmit/Receive buffer register] TB/RB

The transmit buffer and the receive buffer are located at the same

address. The transmit buffer is write-only and the receive buffer is

read-only. If a character bit length is 7-bit, the MSB of data stored in

the receive buffer is “0”.

Fig. 23 Continuous transmission operation of UART serial I/O

[Baud Rate Generator] BRG

The baud rate generator determines the baud rate for serial transfer.

The baud rate generator divides the frequency of the count source

by 1/(n + 1), where n is the value written to the baud rate generator.

TSC=0

TBE=1

TBE=0

ST

SP

ST

SP

ST

1 : When the serial I/O1 mode selection bits (b7, b6) is “10”, the transmit enable bit is “1”, and continuous transmit valid bit is “1”, writing on the

transmit buffer initiates continuous transmission of the same data.

2 : Select 0 for continuous transmit valid bit to stop continuous transmission.

3 : If the transmit buffer contents are rewritten during a continuous transmission, transmission of the rewritten data will be started after

completing transmission of 1 byte.

Notes

1 Start Bit

7 or 8 Data Bit

1 or 0 Parity Bit

1 or 2 Stop Bit

Transmit/Receive Clock

Transmit Buffer Register

Write Signal