PC-SIG Library 8

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Assembly Source File | 1983-02-02 | 10.1 KB | 456 lines

;Version 2.1 1982 Mark S Zachmann ; ; This program lets you totally remap the ; disks on MS-DOS. You can map each side of a logical ; drive to any other side or to memory. ; ; For example, a usual configuration would be ; map drive 0, sides 0,1 to drive 0 sides 0,1 (no change) ; drive 1, sides 0,1 to drive 1 sides 0,1 " ; drive 2, side 0 to segment 4000h ; drive 2, side 1 to segment 6800h ; ; this will let you use 256K for the MS-DOS system, and another ; 320K of memory for a double-sided RAM disk, if you have a 512K ; board installed. ( for 576K total ) ;********************************************** ; to alter this for your system: ; change the equates at locations 'DISKPTR' ; they come in order (0/0, 1/0, 0/1, 1/1, 0/2, 1/2, 0/3, ... ; and each entry says which to map to: ; ; 0h = side 0/disk 0 ; 100h = side 1/disk 0 ; 1h = side 0/disk 1 ; 101h = side 1/disk 1 ; ...etc ; anything bigger than f00h is treated as a location in RAM, ; thus ; 4000h = segment beginning at 4000:0000h ; 6800h = segment beginning at 6800:0000h ; etc ;********************************************* ; also, 0FFFFh = return an error if this side is selected. ; for my default setup: (disk A,B normal, C RAMdisk, ...) ; Note that the dip switches inside must then be set to ; indicate 3 disk drives and 256K of memory. All disk operations ; are transparent to the user. ; this is for two reasons: ;(1) MS-DOS must feel that any RAMdisk memory does not exist ;(2) MS-DOS needs to know how many drives (real or otherwise) ; there are ; Note that the RAM disks must be FORMATted before use, unless ; you use DISKCOPY to send data to them. ; ; ; SYNTAX: ; A>ramdisk creates a ramdisk and writes F6 to each byte ; to eliminate possible parity errors on read ; ; A>ramdisk old creates a ramdisk, but does not overwrite ; old data. used if you had to reset ; (ctrl-alt-del) for some reason TITLE Double-Sided Diskette Support SUBTTL BASE equ 0h ;Base of memory DiskInt equ 4Ch ;Offset of int DISKETTE_STATUS equ 0441h DISK_POINTER equ 078h bufr equ 80h ; command line parm address ;first the macro library must be in here IF1 Include Interupt.MAC ENDIF ;first macro ---- Prolog DOUBLE ASSUME DS:DOUBLE,CS:DOUBLE ;---------------------------------------- ;---------------------------------------- ;---------------------------------------- SUBTTL Diskette I/O Call Entry Point COMMENT * Actual Entry point On entry: DL = logical disk number (0-n) DH = 0 (side-1) On call to disk I/O: DL = physical disk number DH = side number (0 or 1) DH=0 or 1 (1 if DL was odd) For other registers... See Reference Manual p.A-32 IF reference is to memory_disk { Case: RESET - pass to usual disk reset STATUS - " " " READ - transfer buffer to memory WRITE - transfer memory to buffer VERIFY - do nothing (just like BIOS) FORMAT - fill sectors(s) with [DISK_BASE+8] Always return successful completion code. unless signaled otherwise by 0xFFFF assegment } Upon return, all registers except AX unchanged. Memory references also set DISKETTE_STATUS to 0. * ;--------------------------------------------- ; ; Actual diskette I/O filter routine ; ;--------------------------------------------- Main proc far ENTRY: STI ;Allow interrupts push DX ;So we can reset it later cmp AH,1 ;Is it disk independent? jle USUAL ;Yes, do what is usual. ; Now figure out which disk is involved. ; by table lookup. No validity check here. ; The table will return a DX (DH - side, DL - drive) ; value for use or > 3FFh which implies a memory ; reference, in which case the two bytes ; are a starting segment number. ; ** Special Case: ; if address is FFFF hex (impossible, ROM is there) ; we return an error code, so you can use 160K ramdisk ; effectively as single sided disk ; .Most DOS routines try to read side 2, hence this kludge ; for a 160K ramdisk XCHG BX,DX ;Need BX for indexing SHL BL,1 ;*2 for word offset add BL,BH ;side parameter shl BL,1 xor BH,BH MOV BX,CS:[BX+offset DISKPTR] ;address/map xchg BX,DX ;back again cmp DX,0FFFFh ;kludge ? je Doerror ;generate error, for opposite side ;of 160K ramdisk cmp DX,03FFh ;is memory ? ja short MEMdisk ;yes ;---------------------------------------------- ; ;Now call the operating system ; because call requires disk activity ; ;----------------------------------------------- USUAL: pushf ; because OS does IRET ;which wastes a stack item. call cs:disket ;call BIOS ;Return to calling routine ToDOS: pop dx ;old DX value, must be intact ret 2 ;keep flags intact Main endp ;---------------------------------------------- ; ; Use memory for disk ; On entry: DX - starting SEGMENT ; other registers as in BIOS call ; old DX on top of stack ; ; On exit: ; All registers returned ; to normal. AX set to status, and ; DISKETTE_STATUS set to 0. ; Also CY = 0, unless segment was FFFFh ; ; ;----------------------------------------------- Doerror proc near clc cmp AH,5 ;format operation? mov AH,0 je ToDos ;if format, then say OK ;error routine for single mov AX,400h ;sided operation of ramdisk stc jmp short ToDOS ;no need to do the push/pop stuff Doerror endp MEMdisk proc near ;usual memory disk, can't return error ; First calculate the starting address ; DX+CH*100h+CL*20h push DI push SI push DS push ES push CX push BX push AX CLD ;always increment string moves ; if parms change then leave reg's alone xor AX,AX mov AL,CL ;sector dec AX ;relative to 0 mov CL,5 SHL AX,CL ;*20h add AH,CH ;+track*100h add AX,DX ;+segment mov DS,AX ;now DS contains buffer addr pop AX ;get AX back, AL has count push AX xor CX,CX ;how many sectors mov CH,AL ;*256 for words to move ; set up the parameters for DS:SI -> ES:DI ; i.e. a read operation xor SI,SI ; ->0 mov DI,BX ; was ES:BX ; now do the operation cmp AH,3 jb short READ je short WRITE cmp AH,5 jb short VERIF je short FORMAT STC ;unknown, set error flag ;---------------------------------- ; ; Return to DOS by setting status ; to 0 (all OK) and then pop'ing ; registers (leave flags alone) ; ;------------------------------------- Memret label near mov AX,Base mov DS,AX mov BX,DISKETTE_STATUS mov BYTE PTR [BX],0 pop AX pop BX pop CX pop ES pop DS pop SI pop DI mov AH,0 ;Status NEC no problems! CLC ;impossible to get error jmp short ToDOS MEMdisk endp ;-------------------------------------- ; ; Memory I/O routines. ; On Entry: ; ES:DI = DMA address for transfer ; DS:SI - buffer address ; CX = number of words to transfer ; ; On Exit: ; CY = 0 ; ;------------------------------------------ ;---------------------------------- ; ; Memory read ; ;---------------------------------- READ proc near rep movsw jmp short MEMret READ endp ;----------------------------------------- ; ; Memory write ; ; On entry as in read ; ;------------------------------------------ WRITE proc near call REVERS ;backwards move rep movsw jmp short MEMret WRITE endp ;----------------------------------------- ; ; Memory Verify ; note that verify does nothing ; if you look at reference manual ; p.A-34 it is clear that ; verify only tries to read a track! ; which must work here ; ;----------------------------------------- VERIF proc near jmp short MEMret VERIF endp ;--------------------------------------- ; ; Memory Format ; ;----------------------------------------- FORMAT proc near call REVERS ;source backwards mov AX,BASE mov DS,AX mov BX,DISK_POINTER lds BX,dword ptr [BX] mov AL,BYTE PTR [BX+8] ; Format char mov AH,AL ;Dup rep stosw jmp short MEMret FORMAT endp ;----------------------------------- ; ; REVERS ; Change Direction, i.e. ; XCHG DS:SI,ES:DI ; ;------------------------------------ REVERS proc near mov AX,DS mov BX,ES mov ES,AX mov DS,BX xchg DI,SI ret REVERS endp ;-------------------------------------- ; ; Permanent storage area ; ;-------------------------------------- disket LABEL DWORD DW ? DW ? ;you can patch this (before or after assembly) ;or use the 7E and 7F system calls to set this ;on the fly DISKPTR label WORD dw 0,100h,1,101h ;my usual setup dw 4000h,6800h ;C disk is all memory dw 0FFFFh, 0FFFFh ;D disk is error dw 12 dup(0) ;extra ;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ;!! ;!! everything after this is temporary ;!! ;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ;--------------------------------------------- ; This 'subroutine' sets up the operating ; system so that the ENTRY routine ; can map logical disks into physical ; disks and memory. ; ; Store the old interrupt vector 13h ; at an indirect call location 'disket'. ; Then replace the vector ; with the user entry point (ENTRY). ; This has the effect of leaving the ; full user routine in memory until ; there is a warm start. ; ; On entry: ; DS = origin of program segment ; Effect on registers is irrelevant. ; ;------------------------------------------ ; macro --- Epilog 013h,Disket,DOUBLE ;--------------------------------- ; ; Fill Memory Disk areas with zero's ; for parity ; ;----------------------------------- ; if Old then do not fill mov AX,CS:zzarg ; first word at 80h cmp AL,'O' je Nofl cmp AL,'o' ;u/l case je Nofl ; ; must not have been an O ; int 12h ;memory size(K) -> AX mov CL,6 ;*64 shl AX,CL ;gives segment # CLD ;upwards mov BX,AX ;for loop convenience mov DX,0800H ;32K increment FILLUP: mov ES,BX mov AX,0F6F6h xor DI,DI ;from 0 base mov CX,4000h ;words/32k rep stosw mov BX,ES add BX,DX cmp BH,0B0h ;video yet ? jb FILLUP ;------------------------------------ ; ; Configure the disks ; ;--------------------------------------- Nofl: jmp CONFIG HIMSG: db 'Disk reconfiguration program',13,10 db ' 1982, MSZachmann',13,10,'$' ; macro --- Finish DOUBLE,250 end STC ;unknown