HD404828RFS datasheet(91/149 Pages) RENESAS

91 / 149 page

HD404829R Series

Transmit Clock Error Detection (In External Clock Mode): The serial interface will malfunction if a

spurious pulse caused by external noise conflicts with a normal transmit clock during transfer. A transmit

clock error of this type can be detected as shown in figure 73.

If more than eight transmit clocks are input in transfer state, at the eighth clock including a spurious pulse

by noise, the octal counter reaches 000, the serial interrupt request flag (IFS: $023, bit 2) is set, and

transmit clock wait state is entered. At the falling edge of the next normal clock signal, the transfer state is

entered. After the transfer completion processing is performed and IFS is reset, writing to serial mode

therefore the error can be detected.

Notes on Use:

• Initialization after writing to registers: If port mode register A (PMRA: $004) is written to in transmit

clock wait state or in transfer state, the serial interface must be initialized by writing to serial mode

• Serial interrupt request flag (IFS: $023, bit 2) set: If the state is changed from transfer to another by

writing to serial mode register A (SMRA: $005) or executing the STS instruction during the first low

pulse of the transmit clock, the serial interrupt request flag is not set. To set the serial interrupt request

flag, serial mode register A write or STS instruction execution must be programmed to be executed after

confirming that the

SCK pin is at 1, that is, after executing the input instruction to port R2.

Registers for Serial Interface

The serial interface operation is selected, and serial data is read and written by the following registers.

Serial Mode Register A (SMRA: $005)

Serial Mode Register B (SMRB: $028)

Serial Data Register (SRL: $006, SRU: $007)

Port Mode Register A (PMRA: $004)

Miscellaneous Register (MIS: $00C)

Serial Mode Register A (SMRA: $005): This register has the following functions (figure 74).

• R2

1/SCK pin function selection

• Transfer clock selection

• Prescaler division ratio selection

• Serial interface initialization

Serial mode register A (SMRA: $005) is a 4-bit write-only register. It is reset to $0 by MCU reset.

A write signal input to serial mode register A (SMRA: $005) discontinues the input of the transmit clock to

the serial data register and octal counter, and the octal counter is reset to 000. Therefore, if a write is

performed during data transfer, the serial interrupt request flag (IFS: $023, bit 2) is set.

Written data is valid from the second instruction execution cycle after the write operation, so the STS

instruction must be executed at least two cycles after that.

HD404828RFS Datasheet(PDF) 91 Page - Renesas Technology Corp