From 203188e6593efd1e00ae66f787722cf26230db3c Mon Sep 17 00:00:00 2001
From: Jacob Krall <jacob@jkrall.net>
Date: Sun, 4 Oct 2020 01:05:44 -0400
Subject: [PATCH] vdp: printable ASCII

---
 vdp.s | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 143 insertions(+), 13 deletions(-)

diff --git a/vdp.s b/vdp.s
index 171c557..3ec9337 100644
--- a/vdp.s
+++ b/vdp.s
@@ -8,6 +8,10 @@ VDP_REGISTER_BITS = $80
 VDP_NAME_TABLE_BASE = $0000
 VDP_PATTERN_TABLE_BASE = $0800
 
+; zero page addresses
+VDP_PATTERN_INIT = $30
+VDP_PATTERN_INIT_HI = $31
+
   .macro vdp_write_vram
   lda #<(\1)
   sta VDP_REG
@@ -47,29 +51,39 @@ vdp_initialize_pattern_table:
   pha
   phx
   vdp_write_vram VDP_PATTERN_TABLE_BASE
-  ldx #0
+  lda #<vdp_patterns
+  sta VDP_PATTERN_INIT
+  lda #>vdp_patterns
+  sta VDP_PATTERN_INIT_HI
 vdp_pattern_table_loop:
-  lda vdp_hex_digits,x
+  lda (VDP_PATTERN_INIT)
   sta VDP_VRAM
-  inx
-  cpx #(vdp_end_hex_digits - vdp_hex_digits)
+
+  lda VDP_PATTERN_INIT
+  clc
+  adc #1
+  sta VDP_PATTERN_INIT
+  lda #0
+  adc VDP_PATTERN_INIT_HI
+  sta VDP_PATTERN_INIT_HI
+  cmp #>vdp_end_patterns
   bne vdp_pattern_table_loop
+  lda VDP_PATTERN_INIT
+  cmp #<vdp_end_patterns
+  bne vdp_pattern_table_loop
+
   plx
   pla
   rts
 
 vdp_initialize_name_table:
-  ; initialize to "0123456789ABCDEF"
   pha
-  phx
   vdp_write_vram VDP_NAME_TABLE_BASE
   lda #0
 vdp_name_table_loop:
   sta VDP_VRAM
-  ina
-  cmp #$10
-  bne vdp_name_table_loop
-  plx
+  inc
+  bne vdp_name_table_loop ; will be true after $FF
   pla
   rts
 
@@ -91,10 +105,62 @@ vdp_register_3: .byte $00       ; Color table base (currently unused)
 vdp_register_4: .byte $01       ; Pattern table base / $800. $01 = $0800
 vdp_register_5: .byte $00       ; Sprite attribute table base (currently unused)
 vdp_register_6: .byte $00       ; Sprite pattern generator (currently unused)
-vdp_register_7: .byte $B4       ; FG/BG. 4=>Dark blue, B=>Light yellow
+vdp_register_7: .byte $1E       ; FG/BG. 1=>Black, E=>Gray
 vdp_end_register_inits:
 
-vdp_hex_digits:
+  .align 8
+vdp_patterns:
+; line drawing
+  .byte $00,$00,$00,$FF,$FF,$00,$00,$00 ; lr
+  .byte $18,$18,$18,$18,$18,$18,$18,$18 ; ud
+  .byte $00,$00,$00,$F8,$F8,$18,$18,$18 ; ld
+  .byte $00,$00,$00,$1F,$1F,$18,$18,$18 ; rd
+  .byte $18,$18,$18,$F8,$F8,$00,$00,$00 ; lu
+  .byte $18,$18,$18,$1F,$1F,$00,$00,$00 ; ur
+  .byte $18,$18,$18,$FF,$FF,$18,$18,$18 ; lurd
+; <nonsense for debug>
+  .byte $07,$07,$07,$07,$07,$07,$07,$00 ; 07
+  .byte $08,$08,$08,$08,$08,$08,$08,$00 ; 08
+  .byte $09,$09,$09,$09,$09,$09,$09,$00 ; 09
+  .byte $0A,$0A,$0A,$0A,$0A,$0A,$0A,$00 ; 0A
+  .byte $0B,$0B,$0B,$0B,$0B,$0B,$0B,$00 ; 0B
+  .byte $0C,$0C,$0C,$0C,$0C,$0C,$0C,$00 ; 0C
+  .byte $0D,$0D,$0D,$0D,$0D,$0D,$0D,$00 ; 0D
+  .byte $0E,$0E,$0E,$0E,$0E,$0E,$0E,$00 ; 0E
+  .byte $0F,$0F,$0F,$0F,$0F,$0F,$0F,$00 ; 0F
+  .byte $10,$10,$10,$10,$10,$10,$10,$00 ; 10
+  .byte $11,$11,$11,$11,$11,$11,$11,$00 ; 11
+  .byte $12,$12,$12,$12,$12,$12,$12,$00 ; 12
+  .byte $13,$13,$13,$13,$13,$13,$13,$00 ; 13
+  .byte $14,$14,$14,$14,$14,$14,$14,$00 ; 14
+  .byte $15,$15,$15,$15,$15,$15,$15,$00 ; 15
+  .byte $16,$16,$16,$16,$16,$16,$16,$00 ; 16
+  .byte $17,$17,$17,$17,$17,$17,$17,$00 ; 17
+  .byte $18,$18,$18,$18,$18,$18,$18,$00 ; 18
+  .byte $19,$19,$19,$19,$19,$19,$19,$00 ; 19
+  .byte $1A,$1A,$1A,$1A,$1A,$1A,$1A,$00 ; 1A
+  .byte $1B,$1B,$1B,$1B,$1B,$1B,$1B,$00 ; 1B
+  .byte $1C,$1C,$1C,$1C,$1C,$1C,$1C,$00 ; 1C
+  .byte $1D,$1D,$1D,$1D,$1D,$1D,$1D,$00 ; 1D
+  .byte $1E,$1E,$1E,$1E,$1E,$1E,$1E,$00 ; 1E
+  .byte $1F,$1F,$1F,$1F,$1F,$1F,$1F,$00 ; 1F
+; </nonsense>
+  .byte $00,$00,$00,$00,$00,$00,$00,$00 ; ' '
+  .byte $20,$20,$20,$00,$20,$20,$00,$00 ; !
+  .byte $50,$50,$50,$00,$00,$00,$00,$00 ; "
+  .byte $50,$50,$F8,$50,$F8,$50,$50,$00 ; #
+  .byte $20,$78,$A0,$70,$28,$F0,$20,$00 ; $
+  .byte $C0,$C8,$10,$20,$40,$98,$18,$00 ; %
+  .byte $40,$A0,$A0,$40,$A8,$90,$68,$00 ; &
+  .byte $20,$20,$40,$00,$00,$00,$00,$00 ; '
+  .byte $20,$40,$80,$80,$80,$40,$20,$00 ; (
+  .byte $20,$10,$08,$08,$08,$10,$20,$00 ; )
+  .byte $20,$A8,$70,$20,$70,$A8,$20,$00 ; *
+  .byte $00,$20,$20,$F8,$20,$20,$00,$00 ; +
+  .byte $00,$00,$00,$00,$20,$20,$40,$00 ; ,
+  .byte $00,$00,$00,$F8,$00,$00,$00,$00 ; -
+  .byte $00,$00,$00,$00,$20,$20,$00,$00 ; .
+  .byte $00,$08,$10,$20,$40,$80,$00,$00 ; /
   .byte $70,$88,$98,$A8,$C8,$88,$70,$00 ; 0
   .byte $20,$60,$20,$20,$20,$20,$70,$00 ; 1
   .byte $70,$88,$08,$30,$40,$80,$F8,$00 ; 2
@@ -105,10 +171,74 @@ vdp_hex_digits:
   .byte $F8,$08,$10,$20,$40,$40,$40,$00 ; 7
   .byte $70,$88,$88,$70,$88,$88,$70,$00 ; 8
   .byte $70,$88,$88,$78,$08,$10,$E0,$00 ; 9
+  .byte $00,$00,$20,$00,$20,$00,$00,$00 ; :
+  .byte $00,$00,$20,$00,$20,$20,$40,$00 ; ;
+  .byte $10,$20,$40,$80,$40,$20,$10,$00 ; <
+  .byte $00,$00,$F8,$00,$F8,$00,$00,$00 ; =
+  .byte $40,$20,$10,$08,$10,$20,$40,$00 ; >
+  .byte $70,$88,$10,$20,$20,$00,$20,$00 ; ?
+  .byte $70,$88,$A8,$B8,$B0,$80,$78,$00 ; @
   .byte $20,$50,$88,$88,$F8,$88,$88,$00 ; A
   .byte $F0,$88,$88,$F0,$88,$88,$F0,$00 ; B
   .byte $70,$88,$80,$80,$80,$88,$70,$00 ; C
   .byte $F0,$88,$88,$88,$88,$88,$F0,$00 ; D
   .byte $F8,$80,$80,$F0,$80,$80,$F8,$00 ; E
   .byte $F8,$80,$80,$F0,$80,$80,$80,$00 ; F
-vdp_end_hex_digits:
+  .byte $78,$80,$80,$80,$98,$88,$78,$00 ; G
+  .byte $88,$88,$88,$F8,$88,$88,$88,$00 ; H
+  .byte $70,$20,$20,$20,$20,$20,$70,$00 ; I
+  .byte $08,$08,$08,$08,$08,$88,$70,$00 ; J
+  .byte $88,$90,$A0,$C0,$A0,$90,$88,$00 ; K
+  .byte $80,$80,$80,$80,$80,$80,$F8,$00 ; L
+  .byte $88,$D8,$A8,$A8,$88,$88,$88,$00 ; M
+  .byte $88,$88,$C8,$A8,$98,$88,$88,$00 ; N
+  .byte $70,$88,$88,$88,$88,$88,$70,$00 ; O
+  .byte $F0,$88,$88,$F0,$80,$80,$80,$00 ; P
+  .byte $70,$88,$88,$88,$A8,$90,$68,$00 ; Q
+  .byte $F0,$88,$88,$F0,$A0,$90,$88,$00 ; R
+  .byte $70,$88,$80,$70,$08,$88,$70,$00 ; S
+  .byte $F8,$20,$20,$20,$20,$20,$20,$00 ; T
+  .byte $88,$88,$88,$88,$88,$88,$70,$00 ; U
+  .byte $88,$88,$88,$88,$50,$50,$20,$00 ; V
+  .byte $88,$88,$88,$A8,$A8,$D8,$88,$00 ; W
+  .byte $88,$88,$50,$20,$50,$88,$88,$00 ; X
+  .byte $88,$88,$50,$20,$20,$20,$20,$00 ; Y
+  .byte $F8,$08,$10,$20,$40,$80,$F8,$00 ; Z
+  .byte $F8,$C0,$C0,$C0,$C0,$C0,$F8,$00 ; [
+  .byte $00,$80,$40,$20,$10,$08,$00,$00 ; \
+  .byte $F8,$18,$18,$18,$18,$18,$F8,$00 ; ]
+  .byte $00,$00,$20,$50,$88,$00,$00,$00 ; ^
+  .byte $00,$00,$00,$00,$00,$00,$F8,$00 ; _
+  .byte $40,$20,$10,$00,$00,$00,$00,$00 ; `
+  .byte $00,$00,$70,$88,$88,$98,$68,$00 ; a
+  .byte $80,$80,$F0,$88,$88,$88,$F0,$00 ; b
+  .byte $00,$00,$78,$80,$80,$80,$78,$00 ; c
+  .byte $08,$08,$78,$88,$88,$88,$78,$00 ; d
+  .byte $00,$00,$70,$88,$F8,$80,$78,$00 ; e
+  .byte $30,$40,$E0,$40,$40,$40,$40,$00 ; f
+  .byte $00,$00,$70,$88,$F8,$08,$F0,$00 ; g
+  .byte $80,$80,$F0,$88,$88,$88,$88,$00 ; h
+  .byte $00,$40,$00,$40,$40,$40,$40,$00 ; i
+  .byte $00,$20,$00,$20,$20,$A0,$60,$00 ; j
+  .byte $00,$80,$80,$A0,$C0,$A0,$90,$00 ; k
+  .byte $C0,$40,$40,$40,$40,$40,$60,$00 ; l
+  .byte $00,$00,$D8,$A8,$A8,$A8,$A8,$00 ; m
+  .byte $00,$00,$F0,$88,$88,$88,$88,$00 ; n
+  .byte $00,$00,$70,$88,$88,$88,$70,$00 ; o
+  .byte $00,$00,$70,$88,$F0,$80,$80,$00 ; p
+  .byte $00,$00,$F0,$88,$78,$08,$08,$00 ; q
+  .byte $00,$00,$70,$88,$80,$80,$80,$00 ; r
+  .byte $00,$00,$78,$80,$70,$08,$F0,$00 ; s
+  .byte $40,$40,$F0,$40,$40,$40,$30,$00 ; t
+  .byte $00,$00,$88,$88,$88,$88,$78,$00 ; u
+  .byte $00,$00,$88,$88,$90,$A0,$40,$00 ; v
+  .byte $00,$00,$88,$88,$88,$A8,$D8,$00 ; w
+  .byte $00,$00,$88,$50,$20,$50,$88,$00 ; x
+  .byte $00,$00,$88,$88,$78,$08,$F0,$00 ; y
+  .byte $00,$00,$F8,$10,$20,$40,$F8,$00 ; z
+  .byte $38,$40,$20,$C0,$20,$40,$38,$00 ; {
+  .byte $40,$40,$40,$00,$40,$40,$40,$00 ; |
+  .byte $E0,$10,$20,$18,$20,$10,$E0,$00 ; }
+  .byte $40,$A8,$10,$00,$00,$00,$00,$00 ; ~
+  .byte $A8,$50,$A8,$50,$A8,$50,$A8,$00 ; checkerboard
+vdp_end_patterns: