pop,   push,

pop, ( Rd --)

Pop Register from Stack.

This instruction loads register Rd with a byte from the STACK. The Stack Pointer is pre-incremented by 1 before the POP.

push, ( Rd --)

Push Register on Stack.

This instruction stores the contents of register Rr on the STACK. The Stack Pointer is post-decremented by 1 after the PUSH.