Asynchronous Serial Interface (Uart) Mode - NEC mPD789101 User Manual

13.4.2 Asynchronous serial interface (UART) mode

In this mode, the one-byte data following the start bit is transmitted/received and thus full-duplex communication
is possible.
This device incorporates a UART-dedicated baud rate generator that enables communication at the desired transfer
rate from many options. In addition, the baud rate can also be defined by dividing the input clock to the ASCK pin.
The UART-dedicated baud rate generator also can output the 31.25-kbps baud rate that complies with the MIDI
standard.
It is recommended that the ceramic/crystal oscillation be used for the system clock in the UART mode. Because
the frequency deviation is large in RC oscillation, if an internal clock is selected as the source clock for the baud rate
generator, there may be problems in send/receive operations.
(1) Register setting
The UART mode is set by serial operating mode register 20 (CSIM20), asynchronous serial interface mode
register 20 (ASIM20), asynchronous serial interface status register 20 (ASIS20), and baud rate generator
control register 20 (BRGC20).
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CHAPTER 13 SERIAL INTERFACE 20
User's Manual U13045EJ2V0UM00