UPD780138 Datasheet, PDF (377/558 Pages) NEC – 8-Bit Single-Chip Microcontrollers

CHAPTER 17 INTERRUPT FUNCTIONS
17.4.4 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. These
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, IF1H, MK0L, MK0H, MK1L, MK1H, PR0L, PR0H, PR1L, and
PR1H 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. Therefore, even if a maskable interrupt request is generated during execution of the
BRK instruction, the interrupt request is not acknowledged.
Figure 17-11 shows the timing at which interrupt requests are held pending.
Figure 17-11. Interrupt Request Hold
CPU processing
Instruction N
Instruction M
PSW and PC saved, jump Interrupt servicing
to interrupt servicing
program
××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 (instruction request).
User’s Manual U16228EJ2V0UD
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