Commodore Plus 4 - Page 286

274 Machine Language on the Commodore Plus/4
. A7DA 8D F5 07 STA $07F5 Save the returned status register.
. A7DD 60 RTS Return from SYS.
PLA—Pull Accumulator from the Stack
A value is pulled from the stack and placed in the accumulator.
Operation: A t
Addressing Mode
Syntax
Flags Affected: N, Z
Opcode Bytes Cycles
Implied
PLA
68
1
The stack pointer is incremented, and the value it points to is placed in the
accumulator.
Example: This program continuously changes the border color until a key is pressed. The
original color of the border is saved on the stack and retrieved using the PLA
instruction after a key is hit.
. SOOO AD 19 PF LDA $PF19
. 2003 48 PHA
. S004 SO OC SO JSR $SOOC
. 2007 68
PLA
. S008 8D 19 PP STA $FF19
. SOOB 00 BRK
. SOOC EE 19 PP IISTC $FF19
. SOOF SO E4 FF JSR $FFE4
. S013 FO F8 BEQ ISOOC
. S014 60 RTS
Get the current border color.
Save on the stack.
Execute the border color change
subroutine.
Retrieve the original border color
from the stack.
Restore the original border color.
Stop processing.
Increment the border color.
Look for a key hit.
If no key, then go back.
Exit the subroutine.
PLP—Pull Processor Status Register from the Stack
A value is pulled from the stack and placed in the processor status register.
Operation: SR \
Addressing Mode Syntax
Flags Affected: All
Opcode Bytes Cycles
Implied
PLP
28
1