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Program status word (PSW)
The program status word is used to hold the instruction execution results and the current status of the
interrupt requests. The IE flag, used to enable and disable maskable interrupts, is mapped to the PSW.
The PSW can be read and written in 8-bit units, and can be manipulated by using bit manipulation
instructions and dedicated instructions (EI and DI). When a vectored interrupt is acknowledged, the PSW is
automatically saved to the stack, and the IE flag is reset (0).
RESET input sets the PSW to 02H.
Symbol
7
6
PSW
IE
Z
IE
0
Disabled
1
Enabled
298
CHAPTER 16 INTERRUPT FUNCTIONS
Figure 16-5. Program Status Word Configuration
5
4
3
2
1
0
AC
0
0
1
Interrupt acknowledgment enable/disable
User's Manual U15331EJ4V1UD
0
After reset
CY
02H
Used in the execution of ordinary instructions
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