
7.4 Hardware Interrupt
MB90580 Series
Chapter 7: Interrupt
87
7.4.4 Hardware Interrupt Ocurrence When Internal Resource Is Being Accessed
When internal I/O area is being asscessed, the CPU will not response to hardware interrupt immediately,
there will be one instruction delay. Please refer to Chapter 2, section 2.1.3 for details.
7.4.5 Interrupt Inhibit Instruction
If F
2
MC-16LX is executing interrupt inhibit instructions, the CPU will not response to hardware interrupt
request immediately, there will be one instruction delay. Please refer to Chapter 2, section 2.1.3 for details.
7.4.6 Multiple Interrupts
The F
2
MC-16LX CPU supports multiple interrupts. If an interrupt of a higher level occurs while another
interrupt is being processed, control is transferred to the high-level interrupt after the currently executing
instruction is completed. After processing of the high-level interrupt is completed, the original interrupt
processing is resumed. An interrupt of the same or lower level may be generated while another interrupt is
being processed. If this happens, the new interrupt request is suspended until the current interrupt
processing is completed, unless the ILM value or I flag is changed by an instruction. The extended
intelligent I/O service cannot be activated from multiple sources; while an extended intelligent I/O service is
being processed, all other interrupt requests or extended intelligent I/O service requests are suspended.
7.4.7 Register Saving In Stack Upon Interrupt
Figure 7.4.7a Registers saved in stack
7.4.8 Precaution in Using Hardware Interrupt
When there is an hardware interrupt, the interrupt request flag should be cleared before leaving the
corresponding interrupt routine to avoid malfunction.
Some of the resources’ interrupt request flag will be cleared automatically when certain register(s) is(are)
read. In this case, please read those registers to clear the interrupt request flag before leaving the interrupt
routine.
H
L
MSB
LSB
AH
AL
PC
PS
ADB
PCB
DPB
DPR
Register saving upon interrupt
Word (16 bits)
SSP (SSP value before interrupt)
SSP (SSP value after interrupt)