Difference between revisions of "Snippet:KStack"
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(Created page with "<pre> ;=========================================================================== ; KStack Functions ;========================================================================...") |
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; push K onto the stack | ; push K onto the stack | ||
lr A, Ku | lr A, Ku | ||
| − | lr | + | lr D, A ; push high byte of K |
| − | |||
| − | |||
| − | |||
lr A, Kl | lr A, Kl | ||
lr S, A ; push low byte of K | lr S, A ; push low byte of K | ||
| Line 53: | Line 50: | ||
inc ; increment the pointer | inc ; increment the pointer | ||
lr IS, A ; and set the ISAR | lr IS, A ; and set the ISAR | ||
| − | lr A, | + | lr A, I |
lr Kl, A ; load lower byte of K | lr Kl, A ; load lower byte of K | ||
| − | |||
| − | |||
| − | |||
lr A, S | lr A, S | ||
lr Ku, A ; load upper byte of K | lr Ku, A ; load upper byte of K | ||
Latest revision as of 00:44, 5 August 2026
;===========================================================================
; 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, starting
; at r57 and working down. 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
kstack.push:
; get the top of the stack
lisu 7
lisl 7 ; r63, stack pointer
lr A, S
lr IS, A ; load the referenced register
; push K onto the stack
lr A, Ku
lr D, A ; push high byte of K
lr A, Kl
lr S, A ; push low byte of K
; adjust the stack pointer
lr A, IS
ai $ff ; decrease ISAR
lisu 7
lisl 7
lr S, A ; store the adjusted stack pointer in r63
; return from the subroutine
pop
;---------------------------------------------------------------------------
; KStack Pop
;---------------------------------------------------------------------------
; pops register K from the stack using r63 as the stack pointer
; destroys ISAR
kstack.pop:
; retrieve K from the stack
lisu 7
lisl 7
lr A, S ; load the stack pointer into A
inc ; increment the pointer
lr IS, A ; and set the ISAR
lr A, I
lr Kl, A ; load lower byte of K
lr A, S
lr Ku, A ; load upper byte of K
; adjust the stack pointer
lr A, IS
lisu 7
lisl 7
lr S, A ; store the adjusted stack pointer in r63
; return from the subroutine
pop
