BIOS comments
This commit is contained in:
Jeff Parsons
parent
95cef85fa8
commit
5ae447ab49
2 changed files with 68 additions and 51 deletions
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@ -2297,52 +2297,55 @@ x91a1: in al,0x40 ; 000091A1 E440 '.@'
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pop ax ; 000091AE 58 'X'
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ret ; 000091AF C3 '.'
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x91b0: mov dx,0x1f6 ; 000091B0 BAF601 '...'
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mov al,0xa0 ; 000091B3 B0A0 '..'
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out dx,al ; 000091B5 EE '.'
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call xc5af ; 000091B6 E8F633 '..3'
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call x83f9 ; 000091B9 E83DF2 '.=.'
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mov al,0xa8 ; 000091BC B0A8 '..'
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out 0x84,al ; 000091BE E684 '..'
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sti ; 000091C0 FB '.'
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mov dx,0x3f4 ; 000091C1 BAF403 '...'
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in al,dx ; 000091C4 EC '.'
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std ; 000091C5 FD '.'
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std ; 000091C6 FD '.'
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std ; 000091C7 FD '.'
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std ; 000091C8 FD '.'
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std ; 000091C9 FD '.'
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std ; 000091CA FD '.'
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cld ; 000091CB FC '.'
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and al,0xf ; 000091CC 240F '$.'
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or al,al ; 000091CE 0AC0 0x0A,'.'
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jz x91d5 ; 000091D0 7403 't.'
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jmp short x922a ; 000091D2 EB56 '.V'
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;
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; Here's where the first HDC (Hard Disk Controller) activity occurs during power-up.
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;
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x91b0: mov dx,0x1f6 ; 000091B0 select the DRVHD (Drive/Head) register
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mov al,0xa0 ; 000091B3 select Head 0 (bits 0-3) and Drive 0 (bit 4)
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out dx,al ; 000091B5 write register
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call xc5af ; 000091B6 perform some I/O to the FDR (Fixed Disk Register), port 0x3F6
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call x83f9 ; 000091B9 TBD (writes 0xA0, 0xA1, 0xA2, 0xA3, 0xA6 to port 0x84)
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mov al,0xa8 ; 000091BC
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out 0x84,al ; 000091BE
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sti ; 000091C0
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mov dx,0x3f4 ; 000091C1 select the REG_STATUS (Main Status Register) of the FDC
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in al,dx ; 000091C4 read register
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std ; 000091C5
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std ; 000091C6
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std ; 000091C7
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std ; 000091C8
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std ; 000091C9
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std ; 000091CA
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cld ; 000091CB
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and al,0xf ; 000091CC keep only the BUSY bits for drives A,B,C,D
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or al,al ; 000091CE are any of those set?
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jz x91d5 ; 000091D0 no
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jmp short x922a ; 000091D2 yes
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nop ; 000091D4
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nop ; 000091D4 90 '.'
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x91d5: sub sp,byte +0xd ; 000091D5 83EC0D '..',0x0D
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mov bp,sp ; 000091D8 8BEC '..'
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xor ax,ax ; 000091DA 33C0 '3.'
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mov ds,ax ; 000091DC 8ED8 '..'
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les si,[0x78] ; 000091DE C4367800 '.6x.'
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mov ax,0x40 ; 000091E2 B84000 '.@.'
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mov ds,ax ; 000091E5 8ED8 '..'
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mov byte [0x40],0xff ; 000091E7 C6064000FF '..@..'
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call xca03 ; 000091EC E81438 '..8'
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mov byte [bp+0x6],0x0 ; 000091EF C6460600 '.F..'
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mov byte [bp+0x7],0x0 ; 000091F3 C6460700 '.F..'
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call x9293 ; 000091F7 E89900 '...'
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mov byte [bp+0x6],0x1 ; 000091FA C6460601 '.F..'
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call x9293 ; 000091FE E89200 '...'
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mov byte [bp+0x5],0x0 ; 00009201 C6460500 '.F..'
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call xee9c ; 00009205 E8945C '..\'
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mov al,0xaf ; 00009208 B0AF '..'
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out 0x84,al ; 0000920A E684 '..'
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mov dx,0x3f2 ; 0000920C BAF203 '...'
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mov al,0xc ; 0000920F B00C '..'
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out dx,al ; 00009211 EE '.'
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and byte [0x3f],0xf0 ; 00009212 80263F00F0 '.&?..'
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add sp,byte +0xd ; 00009217 83C40D '..',0x0D
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x91d5: sub sp,byte +0xd ; 000091D5
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mov bp,sp ; 000091D8
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xor ax,ax ; 000091DA
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mov ds,ax ; 000091DC
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les si,[0x78] ; 000091DE
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mov ax,0x40 ; 000091E2
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mov ds,ax ; 000091E5
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mov byte [0x40],0xff ; 000091E7
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call xca03 ; 000091EC
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mov byte [bp+0x6],0x0 ; 000091EF
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mov byte [bp+0x7],0x0 ; 000091F3
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call x9293 ; 000091F7 this executes a lot of instructions, but no HDC ports are accessed
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mov byte [bp+0x6],0x1 ; 000091FA
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call x9293 ; 000091FE again, this executes a lot of instructions, but no HDC ports are accessed
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mov byte [bp+0x5],0x0 ; 00009201
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call xee9c ; 00009205
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mov al,0xaf ; 00009208
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out 0x84,al ; 0000920A
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mov dx,0x3f2 ; 0000920C select the REG_OUTPUT (Digital Output Register) of the FDC
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mov al,0xc ; 0000920F select the ENABLE and INT_ENABLE bits of REG_OUTPUT
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out dx,al ; 00009211 update register
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and byte [0x3f],0xf0 ; 00009212
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add sp,byte +0xd ; 00009217
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mov al,0xb3 ; 0000921A B0B3 '..'
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mov ah,al ; 0000921C 8AE0 '..'
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call xb544 ; 0000921E E82323 '.##'
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@ -6670,10 +6673,18 @@ xbd0d: in al,0x64 ; 0000BD0D E464 '.d'
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out 0x60,al ; 0000BD15 E660 '.`'
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mov al,0x25 ; 0000BD17 B025 '.%'
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out 0x84,al ; 0000BD19 E684 '..'
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call x91b0 ; 0000BD1B E892D4 '...'
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mov al,0x26 ; 0000BD1E B026 '.&'
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out 0x84,al ; 0000BD20 E684 '..'
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;
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; Perform some FDC initialization
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;
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call x91b0 ; 0000BD1B
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mov al,0x26 ; 0000BD1E
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out 0x84,al ; 0000BD20
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;
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; Perform some HDC initialization
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;
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call xc390 ; 0000BD22 E86B06 '.k.'
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mov al,0x27 ; 0000BD25 B027 '.',0x27
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out 0x84,al ; 0000BD27 E684 '..'
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mov al,0xec ; 0000BD29 B0EC '..'
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@ -7410,6 +7421,9 @@ xc388: pop si ; 0000C388 5E '^'
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shr ax,cl ; 0000C38D D3E8 '..'
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ret ; 0000C38F C3 '.'
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;
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; HDC initialization
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;
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xc390: mov ax,0x40 ; 0000C390 B84000 '.@.'
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mov ds,ax ; 0000C393 8ED8 '..'
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mov al,0xb0 ; 0000C395 B0B0 '..'
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@ -2,14 +2,17 @@
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# Steps to produce a binary ROM from a JSON-encoded ROM, and then disassemble and re-assemble it.
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#
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FILEDUMP=node ../../../../../../modules/filedump/bin/filedump
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TEXTOUT=node ../../../../../../modules/textout/bin/textout
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all: 1988-01-28-test.rom
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1988-01-28.rom: 1988-01-28.json
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node ../../../../../../modules/filedump/bin/filedump --file=1988-01-28.json --output=1988-01-28.rom --format=rom
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$(FILEDUMP) --file=1988-01-28.json --output=1988-01-28.rom --format=rom
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1988-01-28-test.nasm: 1988-01-28.rom
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ndisasm -o0x8000 -se105h -se05ah -se6ffh -sf025h -sf8aah 1988-01-28.rom > 1988-01-28-test.nasm
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node ../../../../../../modules/textout/bin/textout --file=1988-01-28-test.nasm --nasm > temp.nasm
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$(TEXTOUT) --file=1988-01-28-test.nasm --nasm > temp.nasm
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mv temp.nasm 1988-01-28-test.nasm
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1988-01-28-test.rom: 1988-01-28-test.nasm
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