HD404324FS datasheet(67/103 Pages) RENESAS

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HD404054 Series/HD404094 Series

Serial Interface Operation

Selecting and Changing the Operating Mode: Table 25 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 1A (SM1A: $005) settings; to change the operating mode of serial interface 1, always

initialize the serial interface internally by writing data to serial mode register 1A. Note that serial interface

1 is initialized by writing data to serial mode register 1A. Refer to the following section Registers for

Serial Interface for details.

Pin Setting: The R4

1/SCK1 pin is controlled by writing data to serial mode register 1A (SM1A: $005).

Pins R4

2/SI1 and R4 3/SO1 are controlled by writing data to port mode register A (PMRA: $004).

Refer to

the following section Registers for Serial Interface for details.

Transmit Clock Source Setting: The transmit clock source of serial interface 1 is set by writing data to

serial mode register 1A (SM1A: $005) and serial mode register 1B (SM1B: $028). Refer to the following

section Registers for Serial Interface for details.

Data Setting: Transmit data of serial interface 1 is set by writing data to serial data register 1 (SR1L:

$006, SR1U: $007). Receive data of serial interface 1 is obtained by reading the contents of serial data

The output level of the SO

1 pin is invalid until the first data is output after MCU reset, or until the output

level control in idle states is performed.

Transfer Control: Serial interface 1 is activated by the STS instruction. The octal counter is reset to 000

by the STS instruction, and it increments at the rising edge of the transmit clock for serial interface. When

the eighth transmit clock signal is input or when serial transmission/reception is discontinued, the octal

counter is reset to 000, the serial 1 interrupt request flag (IFS1: $003, bit 2) for serial interface 1 is set, and

the transfer stops.

When the prescaler output is selected as the transmit clock of serial interface 1, the transmit clock

frequency is selected as 4t

cyc to 8192tcyc by setting bits 0 to 2 (SM1A0–SM1A2) of serial mode register 1A

(SM1A: $005) and bit 0 (SM1B0) of serial mode register 1B (SM1B: $028) as listed in table 26.

Table 25

Serial Interface 1 Operating Modes

SM1A

PMRA

Bit 3

Bit 1

Bit 0

Operating Mode

Continuous clock output mode

Transmit mode

Receive mode

Transmit/receive mode

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