This is what I have so far.
UPDATE: Banking registers now confirmed by Jim Bagley
; Disassembly of the file "bitmaps\BMPLOAD" ; ; BMP Port $123b ; bit 0 - Write enable. (banks in 16K from $0000-$3fff) ; bit 1 - bitmap ON ; bit 4 - Layer 2 below spectrum screen ; bit 6-7 - Which 16K bank to page into $0000-$3ffff ; ; On entry, HL = arguments ; ; ; Since dot commands run at $2000, and the Layer 2 is paged into $0000-$3fff ; It needs to have some code above the lower 16K to actually copy into layer 2 ; So copy up the "copy" routine, and it'll page in/out the layer 2 bank ; 2000 226221 ld (HL_Save),hl ; Store HL 2003 216421 ld hl,UploadCode ; Src = 2006 110060 ld de,6000h ; dest = $6000 2009 011f00 ld bc,001fh ; size = 31 bytes 200c edb0 ldir 200e 2a6221 ld hl,(HL_Save) ; get HL back 2011 7c ld a,h 2012 b5 or l ; is hl 0? 2013 2008 jr nz,201dh ; if we have an argument, carry on 2015 213121 ld hl,2131h ; get message 2018 cd1d21 call PrintText ; print the filename 201b 1823 jr Exit ; exit ; Load file....? CopyFilename: 201d 112421 ld de,FileName ; "filename.ext" text - space to store filename? 2020 060c ld b,0ch ; b = $0c (max length of allowed filename - no path it seems) ; Copy, and validate characters in filename 2022 7e ld a,(hl) ; first byte of filename 2023 fe3a cp 3ah ; is it a ":"? End of filename 2025 2810 jr z,EndFilename ; if so end of filename 2027 b7 or a ; 0? 2028 280d jr z,EndFilename ; if so end of filename 202a fe0d cp 0dh ; newline? 202c 2809 jr z,EndFilename ; if so end of filename 202e cb7f bit 7,a ; over 127? 2030 2005 jr nz,EndFilename ; if so end of filename 2032 12 ld (de),a ; copy over to filename cache 2033 23 inc hl ; next src letter 2034 13 inc de ; next dest letter 2035 10eb djnz 2022h ; copy all EndFilename 2037 af xor a ; Mark end of filename 2038 12 ld (de),a ; store filename 2039 dd212421 ld ix,FileName ; get filename base address 203d cd6220 call LoadFile: Exit: 2040 af xor a ; no error 2041 c9 ret ; exit ; esxDOS detect if unit is ready DetectUnit: 2042 af xor a ; Detect if unit is ready 2043 cf rst 08h ; call esxDOS 2044 89 db $89 ; M_GETSETDRV ; Open ; IX= Filename (ASCIIZ) ; B = FA_READ ($01) ; FA_APPEND ($06) ; FA_OVERWRITE ($0C) ; OpenFile: 2045 dde5 push ix ; ix = filename 2047 e1 pop hl ; If a DOT command (rather than normal memory), uses HL not IX 2048 0601 ld b,01h ; b = FA_READ 204a 3e2a ld a,2ah ; a = unknown (a=0 for open) 204c cf rst 08h ; call esxDOS 204d 9a db $9a ; F_Open 204e 325620 ld (2056h),a ; Store file handle (self modify read from file code) 2051 c9 ret ; ; esxDOS command - Read from file - command $9d ; IX = address to load into ; BC = number of bytes to load ; A = file handle ReadBytes: 2052 dde5 push ix ; IX = where to to store data 2054 e1 pop hl ; get address to load into 2055 3e00 ld a,00h ; $00 is self modified 2057 cf rst 08h ; call esxDOS 2058 9d db $9d ; F_Read 2059 c9 ret ; esxDOS command - Close File - command $9b ; A = file handle CloseFile: 205a 3a5620 ld a,(2056h) ; Get open file handle 205d b7 or a ; is it 0? (did it open) 205e c8 ret z ; if file handle is 0, return 205f cf rst 08h ; Call esxDOS 2060 9b db $9b ; F_Close 2061 c9 ret LoadFile: 2062 dde5 push ix ; remember filename 2064 cd4220 call DetectUnit ; detect unit and open...?!?!? 2067 dde1 pop ix ; get filename back 2069 cd4520 call OpenFile ; OpenFile - again?? 206c dd21e720 ld ix,BMPHeader ; Read the BMP file header 2070 013600 ld bc,0036h ; read header ($36 bytes) 2073 cd5220 call ReadBytes 2076 dd218321 ld ix,BitMap ; read block into $2183 207a 010004 ld bc,0400h ; read palette - 1024 bytes 207d cd5220 call ReadBytes ; ; Convert the 24bit palette into a simple RRRGGGBB format ; ConvertBMP: 2080 218321 ld hl,BitMap ; Get buffer address ($2183) 2083 11003f ld de,3f00h ; Dest address of converted palette 2086 0600 ld b,00h ConvertionLoop: 2088 7e ld a,(hl) ; get BLUE byte 2089 23 inc hl ; move on to green 208a c620 add a,20h ; brighten up a bit? (blue is always pretty dark??) 208c 3002 jr nc,SkipSatB ; overflow? 208e 3eff ld a,0ffh ; if overflow, then saturate to $FF SkipSatB: 2090 1f rra ; get top 2 bits only RRRGGGBB 2091 1f rra 2092 1f rra 2093 1f rra 2094 1f rra 2095 1f rra 2096 e603 and 03h ; and store them at the bottom 2098 4f ld c,a ; c holds current byte 2099 7e ld a,(hl) ; get GREEN 209a 23 inc hl ; move onto red 209b c610 add a,10h ; brighten up a bit as well 209d 3002 jr nc,SkipSatG ; if no overflow, skip saturate 209f 3eff ld a,0ffh SkipSatG: 20a1 1f rra ; get 3 bits of green into right place 20a2 1f rra 20a3 1f rra 20a4 e61c and 1ch ; mask off remaining lower bits 20a6 b1 or c ; merge with output byte 20a7 4f ld c,a ; store into output 20a8 7e ld a,(hl) ; get RED 20a9 23 inc hl ; move to next byte of colour (assuming alpha) 20aa c610 add a,10h ; brighten up a bit 20ac 3002 jr nc,SkipSatR ; no overflow? 20ae 3eff ld a,0ffh ; Saturate to $FF SkipSatR 20b0 e6e0 and 0e0h ; keep top 3 bits 20b2 b1 or c ; merge with output pixel 20b3 12 ld (de),a ; store converted pixel 20b4 13 inc de ; move to next ouput pixel 20b5 23 inc hl ; move to next BGRA pixel 20b6 10d0 djnz ConvertionLoop ; c = pixel....?!?!?! 20b8 06c0 ld b,0c0h ; bc=$c000 ConvertUploadLoop: 20ba c5 push bc 20bb dd21003e ld ix,3e00h ; $3e00 = Destination address 20bf 010001 ld bc,0100h ; read 256 bytes of data 20c2 cd5220 call ReadBytes ; Read from file ; ; convert 256 value palette index into actual RGB byte pixel using palette lookup ; 20c5 2e00 ld l,00h ; l = xx (loop counter) CopyLoop: 20c7 263e ld h,3eh ; hl = $3exx 20c9 5e ld e,(hl) ; e = Get palette index 20ca 163f ld d,3fh ; d = $3f palette base address - 256 byte aligned 20cc 1a ld a,(de) ; a = palette value (24bit converted downto 8bit) 20cd 265b ld h,5bh ; hl = $5bxx converted 256 byte buffer 20cf 77 ld (hl),a ; ($5bxx) = converted colour pixel 20d0 263e ld h,3eh ; hl = $3e00 20d2 2c inc l ; do 256 bytes of this.... 20d3 20f2 jr nz,CopyLoop 20d5 c1 pop bc ; bc = $c000 20d6 c5 push bc 20d7 cd0060 call 6000h ; block transfer 256 bytes of the bitmap 20da c1 pop bc 20db 10dd djnz ConvertUploadLoop 20dd 013b12 ld bc,123bh ; Bitmap port 20e0 3e02 ld a,02h ; 2 = enable and visible 20e2 ed79 out (c),a ; switch bitmap layer 2 on 20e4 c35a20 jp 205ah BMPHeader: ds 54 ; $20e7 to $211c PrintText: 211d 7e ld a,(hl) ; get character 211e 23 inc hl ; move to next one 211f b7 or a ; is this 0? 2120 c8 ret z ; if so... end of string 2121 d7 rst 10h ; outchr() 2122 18f9 jr 211dh ; print all characters ; ; Looks like data of some kinds ; FileName: db "filename.ext",0 Message: db ".picloadto load image to background",$d,$00 HL_Save dw 0 ; ; Copied up to $6000 ; UploadCode: 2164 05 dec b ; b = upper byte of memory address 2165 78 ld a,b ; get 256 byte page into a 2166 e63f and 3fh ; ignore top bits 2168 57 ld d,a ; de=$0000-$3ffff 2169 1e00 ld e,00h ; Page bitmap block into lower 16K 216b 78 ld a,b 216c e6c0 and 0c0h ; get the 16K bank to page 216e f601 or 01h ; OR in bank active bit 2170 013b12 ld bc,123bh ; bitmap register 2173 ed79 out (c),a ; map bank into memory perhaps? 2175 21005b ld hl,5b00h ; $5b00 src image chunk 2178 010001 ld bc,0100h ; 256 byte copy (one line) 217b edb0 ldir ; copy up (de=dest) 217d 013b12 ld bc,123bh ; bitmap register 2180 ed69 out (c),l ; l=0, disable current bank and screen 2182 c9 ret BitMap: 2183 00 nop ; file is loaded into here....
