7477 datasheet(21/48 Pages) RENESAS

21 / 48 page

MITSUBISHI MICROCOMPUTERS

7477/ 7478 GROUP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

Serial I/O Control Register SIOCON

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

serial I/O 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 a data transfer.

Serial I/O Status Register SIOSTS

The read-only serial I/O status register consists of seven flags

(bits 0 to 6) which indicate the operating status of the serial I/O

function and various errors.

Three of the flags (bits 4 to 6) are valid only in selected 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

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

the receive buffer full flag is set. Writing to the serial I/O status

respectively). Writing “0” to the serial I/O enable bit SIOE (bit 7 of

the serial I/O control register) also clears all the status flags, in-

cluding the error flags.

All bits of the serial I/O status register are initialized to “0” at reset,

but if the transmit enable bit (bit 4) of the serial I/O control register

has been set to “1”, the transmit shift completion flag (bit 2) and

the transmit buffer empty flag (bit 0) become “1”.

Transmit Buffer/Receive Buffer 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 bits, the MSB of data stored

in the receive buffer is “0”.

Baud Rate Generator BRG

The baud rate generator determines the baud rate for serial trans-

fer.

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.

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