Interrupt Request Hold - NEC 78K0/KD1 Series User Manual

16.4.4 Interrupt request hold

There are instructions where, even if an interrupt request is issued for them while another instruction is being
executed, request acknowledgement is held pending until the end of execution of the next instruction.
instructions (interrupt request hold instructions) are listed below.
• MOV PSW, #byte
• MOV A, PSW
• MOV PSW, A
• MOV1 PSW. bit, CY
• MOV1 CY, PSW. bit
• AND1 CY, PSW. bit
• OR1 CY, PSW. bit
• XOR1 CY, PSW. bit
• SET1 PSW. bit
• CLR1 PSW. bit
• RETB
• RETI
• PUSH PSW
• POP PSW
• BT PSW. bit, $addr16
• BF PSW. bit, $addr16
• BTCLR PSW. bit, $addr16
• EI
• DI
• Manipulation instructions for the IF0L, IF0H, IF1L, MK0L, MK0H, MK1L, PR0L, PR0H, and PR1L registers
Caution The BRK instruction is not one of the above-listed interrupt request hold instructions. However,
the software interrupt activated by executing the BRK instruction causes the IE flag to be cleared
to 0. Therefore, even if a maskable interrupt request is generated during execution of the BRK
instruction, the interrupt request is not acknowledged.
Figure 16-11 shows the timing at which interrupt requests are held pending.
CPU processing
××IF
Remarks 1. Instruction N: Interrupt request hold instruction
2. Instruction M: Instruction other than interrupt request hold instruction
3. The ××PR (priority level) values do not affect the operation of ××IF (interrupt request).
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CHAPTER 16 INTERRUPT FUNCTIONS
Figure 16-11. Interrupt Request Hold
Instruction N Instruction M
Preliminary User's Manual U16315EJ1V0UD
PSW and PC saved, jump Interrupt servicing
to interrupt servicing program
These