Datasheet

PIC18F1220/1320
DS39605F-page 220 © 2007 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
previous 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 = 0x0031A2
Stack (1 level down) = 0x014332
After Instruction
TOS = 0x014332
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 implement-
ing a software stack by modifying
TOS and then pushing 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 = 0x00345A
PC = 0x000124
After Instruction
PC = 0x000126
TOS = 0x000126
Stack (1 level down) = 0x00345A