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CHAPTER 2 CPU
2.10 Interrupt Disable Instructions
Interrupt requests are not sampled for the following ten instructions:
- MOV ILM,#imm8 - PCB - SPB - OR CCR,#imm8 - NCC
- AND CCR,#imm8 - ADB - CMR - POPW PS - DTB
■ Interrupt Disable Instructions
If a valid hardware interrupt request occurs during execution of any of the above instructions, the interrupt
can be processed only when an instruction other than the above is executed. For details, see Figure 2.10-1 .
Figure 2.10-1 Interrupt Disable Instruction
■ Restrictions on Interrupt Disable Instructions and Prefix Instructions
When a prefix code is placed before an interrupt disable instruction, the prefix code affects the first
instruction after the code other than the interrupt disable instruction. For details, see Figure 2.10-2 .
Figure 2.10-2 Interrupt Disable Instructions and Prefix Codes
■ Consecutive prefix codes
When competitive prefix codes are placed consecutively, the latter becomes valid.
In the figure below, competitive prefix codes are PCB, ADB, DTB, and SPB.
For details, see Figure 2.10-3 .
Figure 2.10-3 Consecutive Prefix Codes
• • • • • • • •
(a)
(a)
• • •
Interrupt disable instruction
Ordinary
instruction
Interrupt request
Interrupt acceptance
• • • •
MOV A, FFH
CCR:XXX10XX
NCC ADD A,01
H
CCR:XXX10XX
MOV ILM,#imm8
Interrupt disable instruction
CCR does not change with NCC.
• • • • •• • • • •
ADB DTB PCB ADD A,01H
Prefix code
PCB is valid as the prefix
code.