Broken Pipe
f98e3657d4
Added the reconstructed source code of the boot sector and I/O system (DOS BIOS).
148 lines
2.4 KiB
NASM
148 lines
2.4 KiB
NASM
;This is a disk boot routine for the 1771/1791 type disk
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;controllers. It would normally reside on track 0,
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;sector 1, to be loaded by the "B" command of the
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;monitor at address 200H. By changing the equates
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;below, it may be configured to load any size of
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;program at any address. The program is assumed to
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;occupy consecutive sectors starting at track 0, sector
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;2, and will begin exection at its load address (which
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;must be a 16-byte boundary) with the Instruction
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;Pointer set to zero.
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; Variations are available for the Cromemco 4FDC with
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; large disks, the 4FDC with small disks, the Tarbell
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; single-density controller, and the Tarbell double-
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; density controller. Select one.
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CROMEMCOSMALL: EQU 0
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CROMEMCOLARGE: EQU 1
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TARBELLSINGLE: EQU 0
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TARBELLDOUBLE: EQU 0
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LOAD: EQU 400H ;Address to load program
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SEG: EQU 40H ;LOAD/10H
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SECTOR: EQU 51 ;No. of 128-byte sectors to load
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BOOTER: EQU 200H ;"B" command puts booter here
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;**************************************************************
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CROMEMCO: EQU CROMEMCOLARGE+CROMEMCOSMALL
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TARBELL: EQU TARBELLSINGLE+TARBELLDOUBLE
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WD1771: EQU CROMEMCO+TARBELLSINGLE
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WD1791: EQU TARBELLDOUBLE
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SMALL: EQU CROMEMCOSMALL
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LARGE: EQU CROMEMCOLARGE+TARBELL
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IF SMALL
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MAXSECT:EQU 18
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ENDIF
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IF LARGE
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MAXSECT:EQU 26
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ENDIF
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IF TARBELL
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DISK: EQU 78H
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ENDIF
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IF CROMEMCO
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DISK: EQU 30H
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ENDIF
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IF WD1771
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READCOM:EQU 88H
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ENDIF
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IF WD1791
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READCOM:EQU 80H
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ENDIF
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IF CROMEMCOLARGE
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WAITBYTE:EQU 0B1H
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ENDIF
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IF CROMEMCOSMALL
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WAITBYTE:EQU 0A1H
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ENDIF
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ORG BOOTER
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PUT 100H
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XOR AX,AX
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MOV DS,AX
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MOV ES,AX
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MOV SS,AX
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UP
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MOV DI,LOAD
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MOV DX,SECTOR
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MOV BL,2
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SECT:
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MOV AL,BL
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OUTB DISK+2
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MOV CX,128
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INB DISK+4
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TEST AL,20H
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MOV AL,READCOM
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JNZ OUTCOM
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MOV AL,READCOM+4
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OUTCOM:
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OUTB DISK
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IF CROMEMCO
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MOV AL,WAITBYTE
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OUT DISK+4 ;Turn on hardware wait
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ENDIF
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READ:
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INB DISK+4
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IF TARBELL
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ROL AL
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JNC DONE
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ENDIF
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IF CROMEMCO
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ROR AL
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JC DONE
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ENDIF
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INB DISK+3
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STOB
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LOOP READ
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GETSTAT:
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INB DISK+4
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IF TARBELL
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ROL AL
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JC GETSTAT
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ENDIF
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IF CROMEMCO
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ROR AL
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JNC GETSTAT
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ENDIF
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DONE:
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IN DISK
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AND AL,9CH
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JNZ SECT
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DEC DX
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JZ BOOT
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INC BL
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CMP BL,MAXSECT+1
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JNZ SECT
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XOR BL,BL
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INC DX
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MOV AL,58H ;Step in with update
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OUTB DISK
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JP GETSTAT
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BOOT:
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MOV AX,SEG
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MOV SS,AX
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MOV ES,AX
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MOV DS,AX
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JMP 0,SEG
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