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
register clears all the error flags OE, PE, FE, and SE(bit 3 to bit 6,
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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MITSUBISHI [ Mitsubishi Group ]
