Snippet:KStack

2026-08-04T22:43:21Z

E5frog:

<pre>
;===========================================================================
; KStack Functions
;===========================================================================
; the K stack implements a stack using the registers. it uses r63 as a stack
; pointer that holds the register number of the top of the stack.
; When called, K is pushed to the first two registers on the stack, and the
; pointer is increased.
;
; at startup, the stack pointer (r63) should be set to 62 ($3E)

;---------------------------------------------------------------------------
; KStack Push
;---------------------------------------------------------------------------
; pushes register K onto the stack using r63 as the stack pointer
; destroys ISAR data

pushk:
lisu 7 ; get the top of the stack
lisl 7 ; r63, stack pointer
lr A,S
lr IS, A ; load the referenced register
lr A,KU
lr I,A ; push high byte of K
lr A,KL
lr I,A ; push low byte of K
lr A,IS
lisu 7
lisl 3
lr S,A ; save the register number to the stack pointer
pop

;---------------------------------------------------------------------------
; KStack Pop
;---------------------------------------------------------------------------
; pops register K from the stack using r63 as the stack pointer
; destroys ISAR

popk:
lisu 7 ; r63, stack pointer
lisl 7
lr A,S ; A = stack pointer, points to next free
ai $ff ; A = last pushed byte, KL
lr IS,A ; ISAR -> KL
lr A,D ; read KL, then ISAR -> KU
lr KL,A
lr A,S ; read KU
lr KU,A
lr A,IS ; ISAR now points to new stack pointer
lisu 7
lisl 3
lr S,A ; store new stack pointer in r59
pop
</pre>

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Snippet:KStack