;; #LAYOUT# STD *        #TAKE
;; #LAYOUT# *   KERNAL_0 #TAKE
;; #LAYOUT# *   *        #IGNORE

;
; Official Kernal routine, described in:
;
; - [RG64] C64 Programmers Reference Guide   - page 290
; - [CM64] Computes Mapping the Commodore 64 - page 215
;
; CPU registers that has to be preserved (see [RG64]): none
;


PLOT:

	bcs plot_get

	; Note: the 'set' part has to start from $E50C, as this is a known address
	; - https://www.lemon64.com/forum/viewtopic.php?t=3296&amp%3Bstart=15
	; - https://sys64738.org/2019/05/c64-bedtime-coding-eng-printing-08/
	; - 'Duotris' game calls $E50C during startup screen initialization

plot_set:

	sty PNTR
	stx TBLX

	jsr screen_calculate_pointers

	; FALLTROUGH to save one byte on RTS

plot_get:

	ldy PNTR
	ldx TBLX
	rts