NEC switch User Manual
Page 169
CHAPTER 11 INTERRUPT FUNCTIONS
User’s Manual U12978EJ3V0UD
169
(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.
Figure 11-5. Configuration of Program Status Word
IE
Z
0
AC
0
0
1
CY
PSW
7
6
5
4
3
2
1
0
IE
0
1
02H
Symbol
After reset
Used when normal instruction is executed
Interrupt acknowledgment enabled/disabled
Disabled
Enabled