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Deconstructed the BLTCON configuration

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alpine9000
2016-03-04 09:52:51 +11:00
parent d8c8aef472
commit 7cee716990
2 changed files with 29 additions and 1 deletions
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006.simple_blit/bin/blit.adf
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006.simple_blit/blit.s
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@@ -110,10 +110,38 @@ TC_XPOS equ 16
TC_YPOS equ 16
TC_XPOS_BYTES equ (TC_XPOS)/8
;; BLTCON? configuration
;; http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node011C.html
;; blitter logic function minterm truth table
;; fill in D column for desired function
;; A B C D
;; - - - -
;; 0 0 0 0
;; 0 0 1 0
;; 0 1 0 0
;; 0 1 1 0
;; 1 0 0 1
;; 1 0 1 1
;; 1 1 0 1
;; 1 1 1 1
;;
;; then read D column from bottom up = 1111000 = $f0
;; this is used in the LF? bits
BLIT_LF_MINTERM equ $f0
BLIT_A_SOURCE_SHIFT equ 0
BLIT_DEST equ $100
BLIT_SRCC equ $200
BLIT_SRCB equ $400
BLIT_SRCA equ $800
BLIT_ASHIFTSHIFT equ 12 ;Bit index of ASH? bits
BLIT_BLTCON1 equ 0 ;BSH?=0, DOFF=0, EFE=0, IFE=0, FCI=0, DESC=0, LINE=0
doblit:
movem.l d0-a6,-(sp)
bsr blitWait
move.l #$09f00000,BLTCON0(a6) ;A->D copy, no shifts, ascending mode
move.w #(BLIT_SRCA|BLIT_DEST|BLIT_LF_MINTERM|BLIT_A_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT),BLTCON0(A6)
move.w #BLIT_BLTCON1,BLTCON1(a6)
move.l #$ffffffff,BLTAFWM(a6) ;no masking of first/last word
move.w #0,BLTAMOD(a6) ;A modulo=bytes to skip between lines
move.w #SCREEN_WIDTH_BYTES-TC_WIDTH_BYTES,BLTDMOD(a6) ;D modulo