POP

Pop the top value from the SP stack and assign it to the specified register.

Opcode	Bytes	Cycles	Form	Example
$30	2	3	POP B:_	POP B:1
$31	2	3	POP P:_	POP P:2
$32	2	3	POP I:_	POP I:4
$1A	1	2	POP FP	POP FP
$1B	1	2	POP GP	POP GP
$1C	1	2	POP IP	POP IP
$1D	1	2	POP FLAGS	POP FLAGS

Notes

• The SP stack is commonly used to store local variables and return addresses for function calls.

• The SP stack grows forwards (pushing increases the SP register), whereas the GP stack grows backwards. (The "top" of the GP stack is actually the lowest memory address.)

• POP undoes the action of PUSH.

• For example, the effect of POP P:6 is to add 2 to the SP register, because P:6 is a PAIR register. Then two bytes are read from the memory address indicated by SP and stored in P:6.

• POP IP undoes the action of PUSH RETURN IP. This pair of instructions is used to call subroutines, for example Hybrix function calls.

• POP FLAGS pops the CPU flags as a single byte.

• Aside from the POP FLAGS form, the POP instruction does not affect the CPU condition flags.