HD4046212RFS datasheet(86/157 Pages) RENESAS

86 / 157 page

HD404629R Series

Serial Interface Operation

Selecting and Changing the Operating Mode: Table 28 lists the serial interface’s operating modes. To

select an operating mode, use one of these combinations of port mode register A (PMRA: $004) and serial

mode register A (SMRA: $005) settings; to change the operating mode, always initialize the serial interface

internally by writing data to serial mode register A. Note that the serial interface is initialized by writing

data to serial mode register A. Refer to the following Serial Mode Register A section for details.

Pin Setting: The R21/SCK pin is controlled by writing data to serial mode register A (SMRA: $005). The

R22/SI and R23/SO pins are controlled by writing data to port mode register A (PMRA: $004). Refer to the

following Registers for Serial Interface section for details.

Transmit Clock Source Setting: The transmit clock source is set by writing data to serial mode register A

(SMRA: $005) and serial mode register B (SMRB: $028). Refer to the following Registers for Serial

Interface section for details.

Data Setting: Transmit data is set by writing data to the serial data register (SRL: $006, SRU: $007).

Receive data is obtained by reading the contents of the serial data register. The serial data is shifted by the

transmit clock and is input from or output to an external system.

The output level of the SO pin is invalid until the first data is output after MCU reset, or until the output

level control in idle states is performed.

Table 28 Serial Interface Operating Modes

SMRA

PMRA

Bit 3

Bit 1

Bit 0

Operating Mode

Continuous clock output mode

Transmit mode

Receive mode

Transmit/receive mode

Transfer Control: The serial interface is activated by the STS instruction. The octal counter is reset to

000 by this instruction, and it increments at the rising edge of the transmit clock. When the eighth transmit

clock signal is input or when serial transmission/receive is discontinued, the octal counter is reset to 000,

the serial interrupt request flag (IFS: $023, bit 2) is set, and the transfer stops.

When the prescaler output is selected as the transmit clock, the transmit clock frequency is selected as 4t

cyc

to 8192t

cyc by setting bits 2 to 0 (SMRA2– SMRA0) of serial mode register A (SMRA: $005) and bit 0

(SMRB0) of serial mode register B (SMRB: $028) as listed in table 29.

HD4046212RFS Datasheet(PDF) 86 Page - Renesas Technology Corp