UPD75518 NEC, UPD75518 Datasheet - Page 35

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

3.7 PROGRAM STATUS WORD (PSW): 8 BITS
can be manipulated with a memory manipulation instruction.
The program status word (PSW) consists of various flags closely associated with processor operations.
The PSW is mapped to addresses FB0H and FB1H in the data memory space. The four bits at address FB0H
Save
Restore
Address
Can be manipulated
by an instruction
specifically provided
for controlling this flag
When CALL, CALLA, or CALLF instruction is executed
When hardware interrupt occurs
When RET or RETS instruction is executed
When RETI is executed
CY
Table 3-2 PSW Flags Saved/Restored in Stack Operation
SK2
Cannot be manipulated
Fig. 3-10 Program Status Word Format
FB1H
SK1
SK0
IST1
Can be manipulated
IST0
FB0H
MBE and RBE are saved.
All PSW bits are saved.
MBE and RBE are restored.
All PSW bits are restored.
MBE
Saved/restored flag
RBE
Symbol
PSW
PD75518(A)
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