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CHAPTER 14 8-BIT SERIAL I/O
14.5 Interrupt of 8-Bit Serial I/O
An 8-bit serial I/O interrupt is caused by completion of 8-bit serial data I/O.
■ Interrupt at Serial I/O Operation
In the 8-bit serial I/O, serial output operation and serial input operation are performed at the same time.
When serial I/O transfer is started, the values in the serial data register (SDR) are input and output on a per
bit basis in synchronization with the set shift clock cycle. When the shift clock of the 8th bit rises, the
interrupt request flag bit (SMR: SIOF) is set to "1".
In this case, when the interrupt request output allowance bit is allowed (SMR: SIOE = 1), the interrupt
request (IRQC) for CPU interrupt occurs.
Write "0" to the SIOF bit with the interrupt processing routine and clear the interrupt request. When 8-bit
serial output is completed, the SIOF bit is set irrespective of the SIOE bit value.
If serial I/O transfer stop (SMR: SST = 0) and serial data transfer termination take place at the same time
during serial I/O operation, the interrupt request flag bit (SMR: SIOF = 1). If the SIOE bit is allowed (0 →
1), however, the interrupt request occurs immediately.
■
8-bit Serial I/O Interrupt Register and Vector Table
For interrupt operation, see Section "3.4.2 Steps in the Interrupt Operation ".
Table 14.5-1 8-bit Serial I/O Interrupt Register and Vector Table
Interrupt name
Interrupt level setting register Vector table address
Register Setting bit Higher Lower
IRQC
ILR4 (007E
H
)
LC1 (bit1) LC0 (bit0)
FFE2
H
FFE3
H