M30620FCAFP datasheet(393/615 Pages) RENESAS

393 / 615 page

UART

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-76

(4) How to deal with an error

When receiving data, read an error flag and reception data simultaneously to determine which error

has occurred. If the data read is erroneous, initialize the error flag and the UARTi receive buffer

To initialize the UARTi receive buffer register

1. Set the receive enable bit to “0” (disable reception).

2. Set the receive enable bit to “1” again (enable reception).

To transmit data again due to an error on the reception side, set the UARTi transmit buffer register

again, then transmit the data again.

To set the UARTi transmit buffer register again

1. Set the serial I/O mode select bits to “0002” (invalidate serial I/O).

2. Set the serial I/O mode select bits again.

3. Set the transmit enable bit to “1” (enable transmission), then set transmission data in the UARTi

transmit buffer register.

(5) Functions selection

In operating UART, the following functions can be used:

_______ _______

(a) CTS/RTS function

_______

CTS function is a function in which an external IC can start transmission/reception by means of

_______

inputting an “L” level to the CTS pin. The CTS pin input level is detected when transmission/reception

starts, so if the level is gone to“ H” while transmission/reception is in progress, transmission/recep-

tion stops at the next data.

_______

RTS function is a function to inform an external IC that RTS pin output level has changed to “L” when

_______

reception is ready. RTS regoes to “H” at the falling edge of the transfer clock.

_______ _______

When using clock-asynchronous serial I/O, choose one of three types of CTS/RTS functions.

_______ _______

• CTS/RTS functions disabled

_______ _______

CTS/RTS pin is a programmable I/O port.

_______

• CTS function only enabled

_______ _______

_______

CTS/RTS pin performs the CTS function.

_______

• RTS function only enabled

_______ _______

_______

CTS/RTS pin performs the RTS function.

(b) Sleep mode

Sleep mode is a mode in which data is transferred to a particular microcomputer among those con-

nected by use of clock-asynchronous serial I/O devices.

This function is to reserve data when writing to transmit buffer register or reading from receive buffer

(d) TxD, RxD I/O polarity reverse function

This function receive a polarity of TxD port output level and a polarity of RxD port input level.

(e) Bus collision detection function

This function is to sample the output level of the TxD pin and the input level of the RxD pin at the

rising edge of the transfer clock; if their values are different, then an interrupt request occurs.

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