M30620FCAFP datasheet(369/615 Pages) RENESAS

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Clock-Synchronous Serial I/O

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-52

2.4.1 Overview of the clock-synchronous serial I/O usage

Clock-synchronous serial I/O carries out 8-bit data communications in synchronization with the clock. The

following is an overview of the clock-synchronous serial I/O usage.

(1) Transmission/reception format

8-bit data

(2) Transfer rate

If the internal clock is selected as the transfer clock, the divide-by-2 frequency, resulting from the bit

rate generator division, becomes the transfer rate. The bit rate generator count source can be se-

lected from the following: f1, f8, and f32. Clocks f1, f8, and f32 are derived by dividing the CPU’s main

clock by 1, 8, and 32 respectively.

Furthermore, if an external clock is selected as the transfer clock, the clock frequency input to the CLK

pin becomes the transfer rate.

(3) Error detection

Only overrun error can be detected. Overrun error is an error that occurs when the next data is made

ready before the reception buffer register is read.

(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 serial I/O mode select bit to “0002” (invalid serial I/O).

3. Set the serial I/O mode select bit.

4. 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) Function selection

For clock-synchronous serial I/O, the following functions can be selected:

_______ _______

(a) CTS/RTS function

_______

In the CTS function, an external IC can start transmission/reception by inputting an “H” level to the

_______

CTS pin. The CTS pin input level is detected when transmission/reception starts. Therefore, if the

level is set to “L” during transmission/reception, it will stop from the next data.

_______

The RTS function informs an external IC that RTS is reception-ready and has changed to “L”. RTS

goes to “H” at the falling edge of the transfer clock.

2.4 Clock-Synchronous Serial I/O Usage

M30620FCAFP Datasheet(PDF) 369 Page - Renesas Technology Corp

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