
ML66517 Family User’s Manual
Chapter 12
Serial Port Functions
12 – 11
12.4.3 Example of SIO1-related Register Settings
12.4.3.1 UART Mode Settings
Transmit settings
(1) Port 8 mode register (P8IO)
If TXD1 (transmit data output) is to be used, set bit 1 (P8IO1) to “1” to configure that port as an output. If
the baud rate clock is to be input externally, reset bit 2 (P8IO2) to “0” to configure that port as an input.
(2) Port 8 secondary function control register (P8SF)
If TXD1 (transmit data output) is to be used, set bit 1 (P8SF1) to “1” to configure that port as a secondary
function output. If the baud rate clock is to be input externally, specify with bit 2 (P8SF2) whether the input
will be pulled-up.
(3) SIO1 transmit control register (ST1CON)
Reset bit 0 (ST1MOD) to “0” to change the mode to UART mode. Specify the transmit data length with bit
1 (ST1LN). Specify the stop bit length with bit 3 (ST1STB). Specify whether there is parity with bit 4
(ST1PEN). If parity is selected, specify the parity bit logic with bit 5 (ST1ODD). With bit 6 (TR1MIE),
specify whether interrupt requests are enabled or disabled when a transmit buffer empty signal occurs.
With bit 7 (TR1NIE), specify whether interrupt requests are enabled or disabled when a transmit complete
signal occurs.
(4) SIO1 receive control register (SR1CON)
Specify with bit 2 (S1EXC) whether the baud rate clock is internal (overflow output of timer 4) or external
(RXC1).
(5) SIO1 transmit-receive buffer register (S1BUF)
Transmission is started by writing the transmit data to S1BUF.
Receive settings
(1) Port 8 mode register (P8IO)
If RXD1 (receive data input) is to be used, reset bit 0 (P8IO0) to “0” to configure that port as an input. If the
baud rate clock is to be input externally, reset bit 2 (P8IO2) to “0” to configure that port as an input.
(2) Port 8 secondary function control register (P8SF)
Specify with bit 1 (P8SF0) whether the RXD1 pin will be pulled-up. If the baud rate clock is to be input
externally, specify with bit 2 (P8SF2) whether the input will be pulled-up.
(3) SIO1 receive control register (SR1CON)
Reset bit 0 (SR1MOD) to “0” to change the mode to UART mode. Specify the receive data length with bit 1
(SR1LN). Specify with bit 2 (S1EXC) whether the baud rate clock is internal (overflow output of timer 4)
or external (RXC1). Specify whether there is parity with bit 4 (SR1PEN). If parity is selected, specify the
parity bit logic with bit 5 (SR1ODD). With bit 6 (RC1IE), specify whether interrupt requests are enabled or
disabled when a receive complete signal occurs. If bit 7 (SR1REN) is set to “1”, reception is enabled and
the reception operation is performed when data arrives.