| 1 | ; FLASH GORDON driver
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| 2 | ; Copyright 2012, Adrien Destugues <pulkomandy@gmail.com>
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| 3 | ; This program is distributed under the terms of the MIT licence
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| 4 |
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| 5 | ; Start here.
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| 6 | DI
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| 7 |
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| 8 | ; Move the screen to $8000 or $0000 so we can display things to the user, while
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| 9 | ; C000 will write to the ROM and 4000 will hold the data to write... That could
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| 10 | ; get a bit messy so maybe we will need to use the screen at 4000 as a buffer
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| 11 | ; for the ROM data as well. Or just use a bank for that ?
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| 12 | ; TODO
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| 13 |
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| 14 | ; Map the ROM in
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| 15 | LD BC, 0x7F85
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| 16 | OUT (C),C
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| 17 |
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| 18 | ; ask the user to enable writing
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| 19 | ; TODO
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| 20 |
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| 21 | ; Turns out with the MegaFlash design, we can't both read and write. When the
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| 22 | ; memory is in write mode, reading is disabled. This means we can't identify
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| 23 | ; the chip, or use the data polling features. And we have to go for the
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| 24 | ; worst-case timing given in the datasheet :(
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| 25 |
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| 26 | ; ... anyway, start with erasing the sectors we need.
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| 27 | CALL 0xBD19
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| 28 | LD B, 4
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| 29 | ERASE
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| 30 | PUSH BC
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| 31 |
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| 32 | LD A, 0x80 ; ERASE
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| 33 | CALL send_command
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| 34 |
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| 35 | CALL prepare_command
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| 36 |
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| 37 | LD B,0xDF
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| 38 | LD C,5 ; ROM number to write (FIXME get it as a RSX param)
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| 39 | OUT (C),C
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| 40 |
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| 41 | ; Compute address near start of sector
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| 42 | POP BC
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| 43 | LD A,B
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| 44 | DEC A
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| 45 | SLA A
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| 46 | SLA A
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| 47 |
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| 48 | ADD 0xC0
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| 49 |
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| 50 | LD H,A
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| 51 |
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| 52 | LD E, 0x30
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| 53 | LD (HL), E
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| 54 |
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| 55 | ; This will delay long enough - we need at least 25ms
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| 56 | CALL 0xBD19
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| 57 |
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| 58 | DJNZ ERASE
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| 59 |
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| 60 | ; Ok, now that we erased the 4 sectors we needed, we can write data to them
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| 61 | LD HL, 0xC000
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| 62 | LD IX, 0x4000
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| 63 | PROGRAM
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| 64 | LD A, 0xA0 ; BYTE PROGRAM ; 2 10
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| 65 | PUSH HL ; 3 13
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| 66 | CALL send_command ; 5 18
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| 67 |
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| 68 | LD B,0xDF
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| 69 | LD C,5 ; ROM number to write (FIXME get it as a RSX param)
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| 70 | OUT (C),C
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| 71 |
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| 72 | POP HL
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| 73 |
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| 74 | LD A,(IX + 0)
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| 75 | LD (HL),A ; Write occurs here. Need to wait 20 NOPs before next
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| 76 | ; operation on ROM. Our code is slow enough already !
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| 77 |
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| 78 | INC HL ; 2 2
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| 79 | INC IX ; 3 5
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| 80 | JR NC, PROGRAM ; 3 8
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| 81 |
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| 82 | JR $
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| 83 |
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| 84 | ; Now reuse and adapt the code from OUL guys !
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| 85 | ; TODO
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| 86 |
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| 87 | ; That's all folks !
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| 88 | RET
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| 89 |
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| 90 | ; Helper routines -----------------------------------------------------
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| 91 |
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| 92 | ; Send a command to the ROM. The available commands are :
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| 93 | ;ERASE equ 0x80
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| 94 | IDENTIFY equ 0x90
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| 95 | BYTEPROG equ 0xA0
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| 96 | RESET equ 0xF0
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| 97 |
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| 98 | ; Input: Commend to send in A register
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| 99 | send_command:
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| 100 | ; That code is shared with sector erase which has some tricks
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| 101 | call prepare_command
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| 102 |
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| 103 | ; Select ROM 1 again and write the command to address 0xEAAA
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| 104 | DEC C
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| 105 | OUT (C),C
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| 106 | EX DE,HL
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| 107 | LD (HL), A
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| 108 |
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| 109 | RET
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| 110 |
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| 111 | prepare_command:
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| 112 | ; Select ROM 1
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| 113 | LD BC,0xDF01
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| 114 | LD HL,0xD555
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| 115 | LD DE,0xEAAA
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| 116 |
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| 117 | ; Select ROM 1 and write 0xAA to address 0xD555
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| 118 | OUT (C),C
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| 119 | LD (HL),E
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| 120 |
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| 121 | ; Select ROM 2 and write 0x55 to address 0xEAAA
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| 122 | INC C
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| 123 | OUT (C),C
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| 124 | EX DE,HL
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| 125 | LD (HL), E
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| 126 |
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| 127 | RET
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| 128 |
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| 129 |
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| 130 | ; Print value of A, as 2 hex digits
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| 131 | printhex
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| 132 | PUSH AF
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| 133 | RRA
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| 134 | RRA
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| 135 | RRA
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| 136 | RRA ;divise A par 8
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| 137 | CALL PRNHEX1 ;affiche le premier morceau
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| 138 | POP AF ;r{cup la valeur originale pour la suit
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| 139 | PRNHEX1 ;affiche la valeur de A sur 1 chiffre
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| 140 | ;affiche A sur 1 chiffre en Hexa
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| 141 | AND 0xF ;ne prend que les unit{s
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| 142 | OR A
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| 143 | DAA ;convertit en d{cimal
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| 144 | ADD A,0xF0 ;ajoute 240
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| 145 | ADC A,0x40 ;ajoute 64+le carry (si >15)
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| 146 | ;on a le code ascii du chiffre @ afficher
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| 147 | JP 0xBB5A ;call-ret
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| 148 | ;
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