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CHAPTER 9 8-BIT SERIAL I/O
9.4 8-bit Serial I/O Interrupts
The 8-bit serial I/O can generate interrupt requests after completion of the serial input
and output of the 8-bit data.
■ Interrupt for serial output operation
The 8-bit serial I/O performs the serial input operation and serial output operation at the same time. When
the serial transfer starts, the data in the serial data register (SDR) is input and output one bit at a time,
synchronized with the cycle of the selected shift clock. The interrupt request flag bit (SMR: SIOF) is set to
"1" on the rising edge of the shift clock of the eighth bit.
At this time, an interrupt request (IRQ5) to the CPU is generated if the interrupt request enable bit is
enabled (SMR: SIOE = "1").
Write "0" to the SIOF bit in the interrupt processing routine to clear the interrupt request. The SIOF bit is
set after completing 8-bit serial output, regardless of the SIOE bit value.
Reference:
The interrupt request flag bit is not set (SMR: SIOF = "1") if serial transfer is stopped (SMR: SST =
"0") at the same time as serial data transfer completes for the serial I/O operation. An interrupt request
is generated immediately if the SIOF bit is "1" when the SIOE bit is changed from disabled to enabled
("0" --> "1").
■ Register and vector table for 8-bit serial I/O interrupts
See Section 3.4.2 "Interrupt Processing" for details on the interrupt operation.
Table 9.4-1 Register and vector table for 8-bit serial I/O interrupts
Interrupt
Interrupt level setting register Vector table address
Register Setting bits Upper Lower
IRQ5 ILR2 (007D
H
) L51 (Bit 3) L50 (Bit 2) FFF0
H
FFF1
H