Writing to both the Third Millenium Arcade Board and the Super Sprite.

I wanted to write to the Third Millenium Arcade Board and the Super Sprite, but there's just one problem: The Super Sprite has its addresses at $C0F0 and $C0F1.

You can write to those addresses just fine in machine language with STA $C0F1 but an AppleSoft POKE doesn't work the same.

Applesoft POKE actually executes a STA ($50),Y to address $C0F1, but that actually reads $C0F1 before it writes $C0F1. It's kind of counter intuitive that you would have a read when you're trying to write something, but that's the wacky design of the 6502.

That read has the side effect of resetting the TMS9918A address pointer so when it writes, the TMS9918 thinks you want to specify the low byte of the address pointer. Each time you write $C0F1 it resets that pointer so you never actually finish setting the high byte of address pointer.

So you have to resort to assembly language, and I poke a little routine into memory and then call it. STA absolute doesn't have the same problem as the STA ($50),Y register indirect mode and it will write to $C0F1 properly without reading it first.

This applesoft program is horribly unoptimized, I just wanted something that would work.

It you let it run for a few minutes it will display the following:

(hint: display the frameskip with F11, set the frameskip to 6 with F8/F9 and unthrottle with F10 to speed things up)

./mame64 apple2e -sl4 arcbd -sl7 ssprite

1  DEF  FN LO(X) = ((X / 256) -  INT (X / 256)) * 256: DEF  FN HI(X) =  INT (X / 256)
4  GOTO 100
5  PRINT "REG WRITE: SLOT=";S;" VALUE=";W0;" REG=";W1
6 SB = 49280:S0 = SB + 16 * S:S1 = S0 + 1
7 IP = 16384
8  POKE IP,160 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1): REM  LDA $C0C1
9 IP = IP + 3: POKE IP,160 + 9: POKE IP + 1,W0:IP = IP + 2: REM  LDA #$W0
10  POKE IP,128 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1):IP = IP + 3: REM  STA $C0C1
11 IP = IP + 0: POKE IP,160 + 9: POKE IP + 1,W1:IP = IP + 2: REM LDA #$W1
13 IP = IP + 0: POKE IP,128 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1):IP = IP + 3: REM STA $C0C1   
14  POKE IP,6 * 16:IP = IP + 1: REM 60 RTS
15  CALL 16384
16  RETURN 
50  PRINT "ADDR WRITE SLOT=";S;" VALUE LO=";W0;" HI=";W1
51 SB = 49280:S0 = SB + 16 * S:S1 = S0 + 1:IP = 16384 + 20:I0 = IP
52  POKE IP,160 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1):IP = IP + 3: REM AD LDA $C0C1  
53  POKE IP,160 + 9: POKE IP + 1,W0:IP = IP + 2: REM  A9 LDA #$W0
54  POKE IP,128 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1):IP = IP + 3: REM 8D STA $C0C1    
55  POKE IP,160 + 9: POKE IP + 1,W1:IP = IP + 2: REM  A9 LDA #$W1
56  POKE IP,128 + 13: POKE IP + 1, FN LO(S1): POKE IP + 2, FN HI(S1):IP = IP + 3: REM 8D STA $C0C1  
57  POKE IP,6 * 16:IP = IP + 1: REM 60 RTS
58  CALL I0
59  RETURN 
60  PRINT "DATA WRITE SLOT=";S;" VALUE=";W0
61 SB = 49280:S0 = SB + 16 * S:S1 = S0 + 1:IP = 16384 + 40:I0 = IP
63  POKE IP,160 + 9: POKE IP + 1,W0:IP = IP + 2: REM A9 LDA #$W0
64  POKE IP,128 + 13: POKE IP + 1, FN LO(S0): POKE IP + 2, FN HI(S0):IP = IP + 3: REM 8D STA $C0C0
67  POKE IP,6 * 16:IP = IP + 1: REM 60 RTS
68  CALL I0
69  RETURN 
70  PRINT "DATA READ SLOT=";S;
71 SB = 49280:S0 = SB + 16 * S:S1 = S0 + 1:IP = 16384 + 60:I0 = IP
73  POKE IP,160 + 13: POKE IP + 1, FN LO(S0): POKE IP + 2, FN HI(S0):IP = IP + 3: REM AD LDA C0C0
74  POKE IP,8 * 16 + 13: POKE IP + 1, FN LO(I0 + 18): POKE IP + 2, FN HI(I0 + 18):IP = IP + 3: REM 8D STA +18
77  POKE IP,6 * 16:IP = IP + 1: REM RTS 
78  CALL I0:R0 =  PEEK (I0 + 18): PRINT " VALUE=";R0
79  RETURN 
99  RETURN 
100 S = 4:W0 = 2:W1 = 128 + 0: GOSUB 5
101 S = 4:W0 = 196:W1 = 128 + 1: GOSUB 5
102 S = 4:W0 = 14:W1 = 128 + 2: GOSUB 5
103 S = 4:W0 = 255:W1 = 128 + 3: GOSUB 5
104 S = 4:W0 = 3:W1 = 128 + 4: GOSUB 5
105 S = 4:W0 = 118:W1 = 128 + 5: GOSUB 5
106 S = 4:W0 = 3:W1 = 128 + 6: GOSUB 5
107 S = 4:W0 = 15:W1 = 128 + 7: GOSUB 5
110 S = 7:W0 = 2:W1 = 128 + 0: GOSUB 5
111 S = 7:W0 = 196:W1 = 128 + 1: GOSUB 5
112 S = 7:W0 = 14:W1 = 128 + 2: GOSUB 5
113 S = 7:W0 = 255:W1 = 128 + 3: GOSUB 5
114 S = 7:W0 = 3:W1 = 128 + 4: GOSUB 5
115 S = 7:W0 = 118:W1 = 128 + 5: GOSUB 5
116 S = 7:W0 = 3:W1 = 128 + 6: GOSUB 5
117 S = 7:W0 = 4:W1 = 128 + 7: GOSUB 5
118  FOR I = 0 TO 15:W0 = I:S = 4:W1 = 128 + 7: GOSUB 5:W0 = 15 - I:S = 7:W1 = 128 + 7: GOSUB 5: NEXT :W0 = 15:W1 = 128 + 7:S = 7: GOSUB 5
119 SL(1) = 4:SL(2) = 7: FOR SI = 1 TO 2:S = SL(SI)
120  REM  INITIALIZE NAME TABLE
125 SR = 4:W0 = 0:W1 = 56 + 64: GOSUB 50: FOR J = 0 TO 2: FOR I = 0 TO 255:W0 = I: GOSUB 60: NEXT : NEXT 
126  REM  LOAD PATTERNS
127 SR = 4:W0 = 0:W1 = 64 + 1: GOSUB 50
128  READ CH: PRINT CH: IF CH =  - 1 THEN  RESTORE : GOTO 130
129  FOR I = 0 TO 7: READ W0: GOSUB 60: NEXT I: GOTO 128
130  REM  INITIALIZE COLOR TABLE
131 SR = 4:W0 = 0:W1 = 32 + 64: GOSUB 50: FOR I = 0 TO 6143: PRINT "COL ";I;:W0 = 15 * 16 + 4: GOSUB 60: NEXT 
140  IF S = 4 THEN A$ = "Third Millenium Arcade Board"
145  IF S = 7 THEN A$ = "Synetix Super Sprite"
150 AD = 16 * 256: FOR I = 1 TO  LEN (A$):C =  ASC ( MID$ (A$,I,1))
155  FOR J = 0 TO 7:SR = 4:A0 = (AD + 8 * (I - 1) + J):A1 = J + C * 8:W0 =  FN LO(A1):W1 =  FN HI(A1): GOSUB 50: GOSUB 70:W0 =  FN LO(A0):W1 =  FN HI(A0) + 64: GOSUB 50:W0 = R0: GOSUB 60
160  NEXT J: NEXT I
199  NEXT SI
1000  DATA  32, 0,0,0,0,0,0,0,0
1001  DATA  33, 24,60,60,24,24,0,24,0
1002  DATA  34, 108,108,0,0,0,0,0,0
1003  DATA  35, 108,108,254,108,254,108,108,0
1004  DATA  36, 24,62,96,60,6,124,24,0
1005  DATA  37, 0,198,204,24,48,102,198,0
1006  DATA  38, 56,108,104,118,220,204,118,0
1007  DATA  39, 24,24,48,0,0,0,0,0
1008  DATA  40, 12,24,48,48,48,24,12,0
1009  DATA  41, 48,24,12,12,12,24,48,0
1010  DATA  42, 0,102,60,255,60,102,0,0
1011  DATA  43, 0,24,24,126,24,24,0,0
1012  DATA  44, 0,0,0,0,0,24,24,48
1013  DATA  45, 0,0,0,126,0,0,0,0
1014  DATA  46, 0,0,0,0,0,24,24,0
1015  DATA  47, 3,6,12,24,48,96,192,0
1016  DATA  48, 60,102,110,126,118,102,60,0
1017  DATA  49, 24,56,24,24,24,24,126,0
1018  DATA  50, 60,102,6,28,48,102,126,0
1019  DATA  51, 60,102,6,28,6,102,60,0
1020  DATA  52, 28,60,108,204,254,12,30,0
1021  DATA  53, 126,96,124,6,6,102,60,0
1022  DATA  54, 28,48,96,124,102,102,60,0
1023  DATA  55, 126,102,6,12,24,24,24,0
1024  DATA  56, 60,102,102,60,102,102,60,0
1025  DATA  57, 60,102,102,62,6,12,56,0
1026  DATA  58, 0,24,24,0,0,24,24,0
1027  DATA  59, 0,24,24,0,0,24,24,48
1028  DATA  60, 12,24,48,96,48,24,12,0
1029  DATA  61, 0,0,126,0,0,126,0,0
1030  DATA  62, 48,24,12,6,12,24,48,0
1031  DATA  63, 60,102,6,12,24,0,24,0
1032  DATA  64, 124,198,222,222,222,192,120,0
1033  DATA  65, 24,60,60,102,126,195,195,0
1034  DATA  66, 252,102,102,124,102,102,252,0
1035  DATA  67, 60,102,192,192,192,102,60,0
1036  DATA  68, 248,108,102,102,102,108,248,0
1037  DATA  69, 254,102,96,120,96,102,254,0
1038  DATA  70, 254,102,96,120,96,96,240,0
1039  DATA  71, 60,102,192,206,198,102,62,0
1040  DATA  72, 102,102,102,126,102,102,102,0
1041  DATA  73, 126,24,24,24,24,24,126,0
1042  DATA  74, 14,6,6,6,102,102,60,0
1043  DATA  75, 230,102,108,120,108,102,230,0
1044  DATA  76, 240,96,96,96,98,102,254,0
1045  DATA  77, 130,198,238,254,214,198,198,0
1046  DATA  78, 198,230,246,222,206,198,198,0
1047  DATA  79, 56,108,198,198,198,108,56,0
1048  DATA  80, 252,102,102,124,96,96,240,0
1049  DATA  81, 56,108,198,198,198,108,60,6
1050  DATA  82, 252,102,102,124,108,102,227,0
1051  DATA  83, 60,102,112,56,14,102,60,0
1052  DATA  84, 126,90,24,24,24,24,60,0
1053  DATA  85, 102,102,102,102,102,102,62,0
1054  DATA  86, 195,195,102,102,60,60,24,0
1055  DATA  87, 198,198,198,214,254,238,198,0
1056  DATA  88, 195,102,60,24,60,102,195,0
1057  DATA  89, 195,195,102,60,24,24,60,0
1058  DATA  90, 254,198,140,24,50,102,254,0
1059  DATA  91, 60,48,48,48,48,48,60,0
1060  DATA  92, 192,96,48,24,12,6,3,0
1061  DATA  93, 60,12,12,12,12,12,60,0
1062  DATA  94, 16,56,108,198,0,0,0,0
1063  DATA  95, 0,0,0,0,0,0,0,254
1064  DATA  96, 24,24,12,0,0,0,0,0
1065  DATA  97, 0,0,60,6,30,102,59,0
1066  DATA  98, 224,96,108,118,102,102,60,0
1067  DATA  99, 0,0,60,102,96,102,60,0
1068  DATA  100, 14,6,54,110,102,102,59,0
1069  DATA  101, 0,0,60,102,126,96,60,0
1070  DATA  102, 28,54,48,120,48,48,120,0
1071  DATA  103, 0,0,59,102,102,60,198,124
1072  DATA  104, 224,96,108,118,102,102,230,0
1073  DATA  105, 24,0,56,24,24,24,60,0
1074  DATA  106, 6,0,6,6,6,6,102,60
1075  DATA  107, 224,96,102,108,120,108,230,0
1076  DATA  108, 56,24,24,24,24,24,60,0
1077  DATA  109, 0,0,102,119,107,99,99,0
1078  DATA  110, 0,0,124,102,102,102,102,0
1079  DATA  111, 0,0,60,102,102,102,60,0
1080  DATA  112, 0,0,220,102,102,124,96,240
1081  DATA  113, 0,0,61,102,102,62,6,7
1082  DATA  114, 0,0,236,118,102,96,240,0
1083  DATA  115, 0,0,62,96,60,6,124,0
1084  DATA  116, 16,48,124,48,48,52,24,0
1085  DATA  117, 0,0,204,204,204,204,118,0
1086  DATA  118, 0,0,204,204,204,120,48,0
1087  DATA  119, 0,0,198,214,214,108,108,0
1088  DATA  120, 0,0,99,54,28,54,99,0
1089  DATA  121, 0,0,102,102,102,60,24,112
1090  DATA  122, 0,0,126,76,24,50,126,0
1091  DATA  123, 14,24,24,112,24,24,14,0
1092  DATA  124, 24,24,24,24,24,24,24,0
1093  DATA  125, 112,24,24,14,24,24,112,0
1094  DATA  126, 114,156,0,0,0,0,0,0
1095  DATA  127, 0,0,0,0,0,0,0,0
1096  DATA  -1

The simple routines I poke into memory and call:

4000: 2 writes to C0F1 to set an address, reading C0F1 first to make sure we reset the address register
     It's a register write if the second byte has the hi byte set.
4014: same routine as 4000
     It's an address write if the second byte has bit 6 set, bit 6 clear if just to read.
4028: write to C0F0, write DATA register
403C: read from C0F0, read DATA register

]CALL -151

*4000L

4000-   AD F1 C0    LDA   $C0F1
4003-   A9 0F       LDA   #$0F
4005-   8D F1 C0    STA   $C0F1
4008-   A9 87       LDA   #$87
400A-   8D F1 C0    STA   $C0F1
400D-   60          RTS   
400E-   00          BRK   
400F-   00          BRK   
4010-   00          BRK   
4011-   00          BRK   
4012-   00          BRK   
4013-   00          BRK   
4014-   AD F1 C0    LDA   $C0F1
4017-   A9 00       LDA   #$00
4019-   8D F1 C0    STA   $C0F1
401C-   A9 78       LDA   #$78
401E-   8D F1 C0    STA   $C0F1
4021-   60          RTS   
4022-   00          BRK   
4023-   00          BRK   
*L

4024-   00          BRK   
4025-   00          BRK   
4026-   00          BRK   
4027-   00          BRK   
4028-   A9 78       LDA   #$78
402A-   8D F0 C0    STA   $C0F0
402D-   60          RTS   
402E-   00          BRK   
402F-   00          BRK   
4030-   00          BRK   
4031-   00          BRK   
4032-   00          BRK   
4033-   00          BRK   
4034-   00          BRK   
4035-   00          BRK   
4036-   00          BRK   
4037-   00          BRK   
4038-   00          BRK   
4039-   00          BRK   
403A-   00          BRK   
*L

403B-   00          BRK   
403C-   AD C0 C0    LDA   $C0C0
403F-   8D 4E 40    STA   $404E
4042-   60          RTS   
4043-   00          BRK   
4044-   00          BRK   
4045-   00          BRK   
4046-   00          BRK   
4047-   00          BRK   
4048-   00          BRK   
4049-   00          BRK   
404A-   00          BRK   
404B-   00          BRK   
404C-   00          BRK   
404D-   00          BRK   
404E-   00          BRK   
404F-   00          BRK   
4050-   00          BRK   
4051-   00          BRK   
4052-   00          BRK