NEC 78K0/KB1+, Preliminary User'S Manual

Page: 292 / 405

CHAPTER 14 INTERRUPT FUNCTIONS
Preliminary User’s Manual U16846EJ1V0UD
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14.4.4 Interrupt request hold
There are instructions where, even if an interrupt request is issued for them while another instruction is being
executed, request acknowledgment 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
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MOV PSW, A
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MOV1 PSW. bit, CY
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MOV1 CY, PSW. bit
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AND1 CY, PSW. bit
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OR1 CY, PSW. bit
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XOR1 CY, PSW. bit
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SET1 PSW. bit
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CLR1 PSW. bit
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RETB
•
RETI
•
PUSH PSW
•
POP PSW
•
BT PSW. bit, $addr16
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BF PSW. bit, $addr16
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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 14-11 shows the timing at which interrupt requests are held pending.
Figure 14-11. Interrupt Request Hold
Instruction N Instruction M
PSW and PC saved, jump
to interrupt servicing Interrupt servicing
program
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).