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7480 Group and 7481 Group User's Manual

1-125

1.14 Serial I/O

HARDWARE

Using Serial I/O Transmit Interrupt and Serial I/O Receive Interrupt

Set the associated registers in the following sequence to use serial I/O transmit interrupt.

Clear the serial I/O transmit interrupt enable bit of interrupt control register 1 to ‘0’.

Set the serial I/O control register.

Execute one or more instructions such as NOP.

Clear the serial I/O transmit interrupt request bit of interrupt request register 1 to ‘0’.

Set the serial I/O transmit interrupt enable bit of interrupt control register 1 to ‘1’.

REASONS 1: If normal port pins are switched to serial I/O pins with the serial I/O control register,

the serial I/O transmit interrupt request bit may become ‘1’.

2: If the transmit enable bit of the serial I/O control register is set to ‘1’, the transmit

buffer empty flag and the transmit shift completion flag are ‘1’. As a result, the serial

I/O transmit interrupt request bit becomes ‘1’ regardless of the state of the transmit

interrupt source selection bit of the serial I/O control register, and the interrupt

request is generated.

Set the associated registers in the following sequence to use serial I/O receive interrupt.

Clear the serial I/O receive interrupt enable bit of interrupt control register 1 to ‘0’.

Set the serial I/O control register.

Execute one or more instructions, such as NOP.

Clear the serial I/O receive interrupt request bit of interrupt request register 1 to ‘0’.

Set the serial I/O receive interrupt enable bit of interrupt control register 1 to ‘1’.

REASON: If normal port pins are switched to serial I/O pins with the serial I/O control register, the

serial I/O receive interrupt request bit may become ‘1’.

7480 Datasheet(PDF) 142 Page - Renesas Technology Corp