UPD78F0138 NEC, UPD78F0138 Datasheet - Page 373

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

17.4.2 Software interrupt request acknowledgement
disabled.
status word (PSW), then program counter (PC), the IE flag is reset (0), and the contents of the vector table (003EH,
003FH) are loaded into the PC and branched.
CPU processing
CPU processing
Remark 1 clock: 1/f
Remark 1 clock: 1/f
A software interrupt acknowledge is acknowledged by BRK instruction execution. Software interrupts cannot be
If a software interrupt request is acknowledged, the contents are saved into the stacks in the order of the program
Restoring from a software interrupt is possible by using the RETB instruction.
Caution Do not use the RETI instruction for restoring from the software interrupt.
(
(
(
(
PR = 1)
PR = 0)
PR = 1)
PR = 0)
IF
IF
IF
IF
Figure 17-9. Interrupt Request Acknowledgement Timing (Maximum Time)
Figure 17-8. Interrupt Request Acknowledgement Timing (Minimum Time)
CPU
CPU
(f
(f
Instruction
Instruction
CPU
CPU
: CPU clock)
: CPU clock)
CHAPTER 17 INTERRUPT FUNCTIONS
User’s Manual U16228EJ2V0UD
Divide instruction
Instruction
25 clocks
33 clocks
32 clocks
8 clocks
PSW and PC saved,
jump to interrupt
servicing
PSW and PC saved,
jump to interrupt
servicing
7 clocks
6 clocks
6 clocks
Interrupt servicing
program
Interrupt servicing
program
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