Provided both algorithm and table
Michael
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Home.md
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@ -8,9 +8,9 @@ Welcome to the AppleWin wiki!
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Given:
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y = abcd efgh
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y = abcd efgh (Range 0 .. 191 = $00 .. $BF)
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Address is then:
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Address of the scanline is calculated via:
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---- ---- abcd efgh INPUT: Y
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---- ---- ---- -fgh &7
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@ -30,7 +30,7 @@ Address is then:
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---- ---- ---a b--- y/64 * 8
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+ ---- ---- -aba b--- y/64*0x28 See Note for alt. * 0x28
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-PP- ---- 0000 0000 Graphics page, $20 or $40
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0PP- ---- 0000 0000 Graphics page, $20 or $40
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= 0PPf ghcd eaba b000 Address
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@ -47,15 +47,130 @@ C code:
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6502 code:
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```assembly
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ORG $900
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0900: B9 00 10 Y2HGRADR LDA YHgrLo, Y
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0903: 85 26 STA GBASL
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0905: B9 00 11 LDA YHgrHi, Y
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0908: 44 E6 ORA $E6
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090A: 85 27 STA GBASH
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090C: 60 RTS
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GBASL EQU $26
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GBASH EQU $27
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HPAG EQU $E6 ; Used by Applesoft, 20 HGR1, 40 HGR2
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ORG $F417
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; Algorithm Y to HGR address
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; INPUT: A = row (0 .. 191)
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; The normal entry point is HPOSN $F411, A=row, Y,X=col
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; F411: STA $E2
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; F413: STX $E3
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; F415: STY $E1
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F417: Y2HGRAddr
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F417: 48 PHA ; Y = abcdefgh
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F418: 29 C0 AND #$C0 ; A = ab000000
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F41A: 85 26 STA GBASL ;
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F41C: 4A LSR ; A = 0ab00000
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F41D: 4A LSR ; A = 00ab0000
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F41E: 05 26 ORA GBASL ; = abab0000
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F420: 85 26 STA GBASL
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F422: 68 PLA ; C A GBASH GBASL
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F423: 85 27 STA GBASH ; ? abcdefgh abcdefgh abab0000
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F425: 0A ASL ; a bcdefgh0 abcdefgh abab0000
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F426: 0A ASL ; b cdefgh00 abcdefgh abab0000
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F427: 0A ASL ; c defgh000 abcdefgh abab0000
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F428: 26 27 ROL GBASH ; a defgh000 bcdefghc abab0000
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F42A: 0A ASL ; d efgh0000 bcdefghc abab0000
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F42B: 26 27 ROL GBASH ; b efgh0000 cdefghcd abab0000
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F42D: 0A ASL ; e fgh00000 cdefghcd abab0000
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F42E: 66 26 ROR GBASL ; 0 fgh00000 cdefghcd eabab000
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F430: A5 27 LDA GBASH ; 0 cdefghcd cdefghcd eabab000
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F432: 29 1F AND #$1F ; 0 000fghcd cdefghcd eabab000
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F434: 05 E6 ORA HPAG ; 0 pppfghcd cdefghcd eabab000
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F436: 85 27 STA GBASH ; 0 pppfghcd pppfghcd eabab000
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y2hgrL EQU $1000
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y2hgrH EQU $1100
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ORG $0900
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; Table Y to HGR address
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; INPUT: Y = row (0 .. 191)
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0900: B9 00 10 Y2HGRADR LDA y2hgrL, Y
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0903: 85 26 STA GBASL
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0905: B9 00 11 LDA y2hgrH, Y
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0908: 44 E6 ORA HPAG ; #$20 for HGR1, #$40 for HGR2
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090A: 85 27 STA GBASH
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090C: 60 RTS
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ORG $1000
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1000: 00 00 00 00 00 00 00 00
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1008: 80 80 80 80 80 80 80 80
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1010: 00 00 00 00 00 00 00 00
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1018: 80 80 80 80 80 80 80 80
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1020: 00 00 00 00 00 00 00 00
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1028: 80 80 80 80 80 80 80 80
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1030: 00 00 00 00 00 00 00 00
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1038: 80 80 80 80 80 80 80 80
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1040: 28 28 28 28 28 28 28 28
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1048: A8 A8 A8 A8 A8 A8 A8 A8
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1050: 28 28 28 28 28 28 28 28
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1058: A8 A8 A8 A8 A8 A8 A8 A8
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1060: 28 28 28 28 28 28 28 28
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1068: A8 A8 A8 A8 A8 A8 A8 A8
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1070: 28 28 28 28 28 28 28 28
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1078: A8 A8 A8 A8 A8 A8 A8 A8
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1080: 50 50 50 50 50 50 50 50
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1088: D0 D0 D0 D0 D0 D0 D0 D0
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1090: 50 50 50 50 50 50 50 50
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1098: D0 D0 D0 D0 D0 D0 D0 D0
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10A0: 50 50 50 50 50 50 50 50
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10A8: D0 D0 D0 D0 D0 D0 D0 D0
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10B0: 50 50 50 50 50 50 50 50
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10B8: D0 D0 D0 D0 D0 D0 D0 D0
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ORG $1100
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1100: 00 04 08 0C 10 14 18 1C
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1108: 00 04 08 0C 10 14 18 1C
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1110: 01 05 09 0D 11 15 19 1D
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1118: 01 05 09 0D 11 15 19 1D
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1120: 02 06 0A 0E 12 16 1A 1E
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1128: 02 06 0A 0E 12 16 1A 1E
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1130: 03 07 0B 0F 13 17 1B 1F
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1138: 03 07 0B 0F 13 17 1B 1F
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1140: 00 04 08 0C 10 14 18 1C
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1148: 00 04 08 0C 10 14 18 1C
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1150: 01 05 09 0D 11 15 19 1D
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1158: 01 05 09 0D 11 15 19 1D
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1160: 02 06 0A 0E 12 16 1A 1E
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1168: 02 06 0A 0E 12 16 1A 1E
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1170: 03 07 0B 0F 13 17 1B 1F
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1178: 03 07 0B 0F 13 17 1B 1F
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1180: 00 04 08 0C 10 14 18 1C
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1188: 00 04 08 0C 10 14 18 1C
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1190: 01 05 09 0D 11 15 19 1D
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1198: 01 05 09 0D 11 15 19 1D
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11A0: 02 06 0A 0E 12 16 1A 1E
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11A8: 02 06 0A 0E 12 16 1A 1E
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11B0: 03 07 0B 0F 13 17 1B 1F
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11B8: 03 07 0B 0F 13 17 1B 1F
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```
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## = Address to Y =
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0PPfghcdeabab000 ab
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PPfghcdeabab0000 << 1
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11000000 & 0xC0
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0PPfghcdeabab000 cde
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0PPfghcdeaba >> 4
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0111000 & 0x38
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0PPfghcdeabab000 fgh
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0PPfgh >> 10
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0111 & 7
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C code:
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y = ((address & 0x18) << 3) | ((address & 0x1c00) >> 10) | ((address & 0x380) >> 4);
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int HGR_address_to_y( int address ) {
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return ((address << 1) & 0xC0) // ab
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| ((address >> 4) & 0x38) // cde
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| ((address >> 10) & 0x07);// fgh
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}
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# TEXT
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## Row to Address
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