27
3886 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
(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 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 memory. Since the shift reg-
ister 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. 23 Block diagram of UART serial I/O1
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