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(4) Program status word (PSW)
The program status word is a register used to hold the instruction execution result and the current status for
interrupt requests. The IE flag to set maskable interrupt enable/disable is mapped here.
Besides 8-bit unit read/write, this register can carry out operations with bit manipulation instructions and
dedicated instructions (EI, DI). When a vectored interrupt is acknowledged, the PSW is automatically saved into
a stack, and the IE flag is reset to 0.
RESET input sets the PSW to 02H.
7
6
5
Symbol
PSW
IE
Z
0
IE
Disabled
0
Enabled
1
CHAPTER 11
INTERRUPT FUNCTIONS
Figure 11-5. Configuration of Program Status Word
4
3
2
1
AC
0
0
1
CY
Interrupt acknowledgment enabled/disabled
User's Manual U12978EJ3V0UD
After reset
0
02H
Used when normal instruction is executed
169
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