Datasheet

PIC18FXX2
DS39564C-page 240 © 2006 Microchip Technology Inc.
POP Pop Top of Return Stack
Syntax: [ label ] POP
Operands: None
Operation: (TOS) → bit bucket
Status Affected: None
Encoding:
0000 0000 0000 0110
Description: The TOS value is pulled off the
return stack and is discarded. The
TOS value then becomes the previ-
ous value that was pushed onto the
return stack.
This instruction is provided to
enable the user to properly manage
the return stack to incorporate a
software stack.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
POP TOS
value
No
operation
Example:
POP
GOTO NEW
Before Instruction
TOS = 0031A2h
Stack (1 level down) = 014332h
After Instruction
TOS = 014332h
PC = NEW
PUSH Push Top of Return Stack
Syntax: [
label ] PUSH
Operands: None
Operation: (PC+2) → TOS
Status Affected: None
Encoding:
0000 0000 0000 0101
Description: The PC+2 is pushed onto the top of
the return stack. The previous TOS
value is pushed down on the stack.
This instruction allows to implement
a software stack by modifying TOS,
and then push it onto the return
stack.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode PUSH PC+2
onto return
stack
No
operation
No
operation
Example:
PUSH
Before Instruction
TOS = 00345Ah
PC = 000124h
After Instruction
PC = 000126h
TOS = 000126h
Stack (1 level down) = 00345Ah