þa‹Rþw &þ m^9þhý oPþ nSystem-wide$symbols $xref NAME MCSFEC data struc oldBP DW ? ; space for BP retAdd DW ? ; caller's return address pEDCBlock DD ? ; parameters passed to us pReturnData DD ? pTDCData DD ? data ends dsa struc old_BP DW ? ; and the base pointer return DW ? ; the return address pOutData DD ? pInData DD ? dsa ends extrn edc:byte CGroup GROUP Code ASSUME cs:cGroup CODE segment public 'CODE' public UNTDC ; ; calling sequence for UNTDC: ; CALL UNTDC (pTDCData, pReturnData, pEDCBlock); ; DECLARE (pTDCData, pReturnData, pEDCBlock) POINTER; ; ; TDCData is 24 bytes of 8 bit TDCed (data plus EDC) ; ReturnData is 16 bytes of 7 bit characters (high order bit zero) ; EDCBlock is 16 bytes of 5 bit EDC values (high order bits zero) ; UNTDC PROC near push bp mov bp,sp push ds les si,[bp].pTDCData ; ES:SI = pTDCData lds di,[bp].pReturnData ; DS:DI = pReturnData mov cx,1 ; for edc loop push cx xor ax,ax mov cx,8 push cx zeroArray: mov ds:[di],ax ; zero out ActualData area inc di ; di points @ end of table inc di loop zeroArray pop cx push di ; save di for Ascii data lds di,[bp].pEDCBlock ; get address for UNedc area zeroEDC: mov ds:[di],ax ; zero the edc area inc di inc di loop zeroEDC dec di ; adjust di for end of block xchg di,bx pop di push bx ; save edc ptr for below ; begin unTDCing the ascii data dec di ; adjust di for end of Ascii nextColumn: mov bx,7 ; bit count nextByte: add si,13 ; si points to end of tdc area mov cx,7 nextBit: mov al,es:[si] ; get byte j of tdc'd data xchg cx,bx shr al,cl ;get bit i of byte j to undo xchg cx,bx and al,1 jz zero dec cx shl al,cl ; move bit to correct weight inc cx or ds:[di],al ;store bit in output array zero: sub si,2 loop nextBit inc si dec di ; point to next byte sub bx,1 jnc nextbyte ; now unTDC the EDC data mov dx,7 pop bx ; bx contains di from above push di ; save Ascii pointers push si xchg di,bx add si,13 ; set indexes for EDC data UNedc: add si,10 ; adjust si to end of tdc'd edc mov cx,4 ; only 5 edc bits per byte UNedc1: mov al,es:[si] ; byte j of edc code xchg dx,cx shr al,cl xchg dx,cx and al,1 jz around shl al,cl or ds:[di],al ; store bit in edc array around: sub si,2 sub cx,1 ; move to next bit weight jnc UNedc1 dec di sub dx,1 ; DX keeps track of whether jnc UNedc ; we are doing the even or odd bytes xchg di,bx pop si ; get indexes for Ascii data dec si pop di pop dx sub dx,1 push dx push bx jnc nextColumn pop bx pop dx pop ds pop bp ret 12 ; remove ptrs passed in UNTDC endp public TDC ; ; calling sequence ; CALL TDC (pInData, pOutData); ; DECLARE (pInData, pOutData) POINTER; ; ; InData is 16 bytes of 7 bit characters (high order bit ignored) ; OutData is 24 bytes of 8 bit TDCed (data plus EDC) ; ; requires the external data block "edc", ; which contains edc values for bytes. ; (kept in BitRoutines.plm) ; TDC proc near push bp mov bp,sp push ds les si,[bp].pOutData ; initialize output data to zero xor ax,ax ; zero ax mov cx,12 ; zero out 12 words zloop: mov es:[si],ax inc si ; point to the next word inc si loop zloop les si,[bp].pInData ; get pInData add si,15 ; start at end of table mov cx,16 ; for i:=16 downto 0 ; 16 to 1 for LOOP instruction iloop1: dec cx ; make (16 to 1) into (15 to 0) mov bx,cx ; save I for bottom of loop push bx lds di,[bp].pOutData ; get pOutData ; shr cx,3 ; I div 8 shr cx,1 shr cx,1 shr cx,1 add di,cx push di ; save base + I div 8 add di,12 mov cx,7 ; for j:=0 to 6 jloop1: dec cx ; as for I loop mov al,es:[si] ; get Ith byte of ActualData shr al,cl ; get the Jth bit and al,1 jz jloop11 ; we save time if there isn't a bit to ; shift xchg bx,cx push cx and cx,7 ; I mod 8 shl al,cl ; shift by I mod 8 pop cx xchg bx,cx or ds:[di],al ; store the bit jloop11: sub di,2 ; move down in the table (this is ; faster than DEC, DEC) inc cx ; (6 to 0) to (7 to 1) loop jloop1 pop di ; get base + I div 8 add di,22 ; + 2*J mov al,es:[si] ; ActualData[I] and ax,07fh push bx push es mov bx,ax mov ax,seg edc mov es,ax mov dh,es:edc[bx] pop es pop bx mov cx,5 ; for j:=11 downto 7 jloop2: dec cx mov dl,dh ; get edc byte shr dl,cl ; get the Jth bit and dl,1 jz jloop21 ; don't shift if no bit xchg bx,cx ; (bit j) at (bit I mod 8) push cx and cx,7 ; I mod 8 shl dl,cl ; put (bit J) at (I mod 8) pop cx xchg bx,cx or ds:[di],dl ; store the bit jloop21: sub di,2 ; move down table inc cx loop jloop2 dec si ; move down in ActualData pop cx inc cx loop iloop1 pop ds pop bp ret 8 ; remove parameters TDC endp public C8TO7 ; ; calling sequence ; CALL C8TO7 (pInData, pOutData); ; DECLARE (pInData, pOutData) POINTER; ; ; InData is 14 bytes of 8 bit characters ; OutData is 16 bytes of 7 bit characters (high order bit zero) ; C8TO7 proc near push bp mov bp,sp push ds lds si,[bp].pInData ; get pInData les di,[bp].pOutData ; get pOutData xor bx,bx ; zero bx to accumulate high order bits in mov cx,7 ; do c8to7loop1 for first 7 input bytes c8to7loop1: mov al,ds:[si] ; get 8 bit InData[i], for i := 1 to 7 inc si ; next input byte mov ah,al ; copy byte to work space and ah,80h ; isolate high order bit or bl,ah ; copy bit into first accumulate byte shr bl,1 ; order accumulated bits low to high order and al,7Fh ; zero out high order bit mov es:[di],al ; put 7 bit byte into output inc di ; next output byte loop c8to7loop1 mov cx,7 ; do c8to7loop2 for second 7 input bytes c8to7loop2: mov al,ds:[si] ; get 8 bit InData[i], for i := 8 to 14 inc si ; next input byte mov ah,al ; copy byte to work space and ah,80h ; isolate high order bit or bh,ah ; copy bit into second accumulate byte shr bh,1 ; order accumulated bits low to high order and al,7Fh ; zero out high order bit mov es:[di],al ; put 7 bit byte into output inc di ; next output byte loop c8to7loop2 mov es:[di],bx ; put 2 accumulate bytes on end of output pop ds pop bp ret 8 ; remove parameters c8to7 endp public C7TO8 ; ; calling sequence ; CALL C7TO8 (pInData, pOutData); ; DECLARE (pInData, pOutData) POINTER; ; ; InData is 16 bytes of 7 bit characters (high order bit ignored) ; OutData is 14 bytes of 8 bit characters ; C7TO8 proc near push bp mov bp,sp push ds lds si,[bp].pInData ; get pInData les di,[bp].pOutData ; get pOutData mov bx,ds:[si+14] ; load 2 bytes holding the high order bits mov cx,7 ; do C7TO8loop1 for first 7 input bytes C7TO8loop1: mov al,ds:[si] ; get 7 bit InData[i], for i := 1 to 7 inc si ; next input byte ror bl,1 ; put next high bit into correct position mov ah,bl ; copy byte to work space and ah,80h ; isolate the desired bit or al,ah ; put the high bit back on the byte mov es:[di],al ; put 8 bit byte into output inc di ; next output byte loop C7TO8loop1 mov cx,7 ; do C7TO8loop2 for second 7 input bytes C7TO8loop2: mov al,ds:[si] ; get 7 bit InData[i], for i := 8 to 14 inc si ; next input byte ror bh,1 ; put next high bit into correct position mov ah,bh ; copy byte to work space and ah,80h ; isolate the desired bit or al,ah ; put the high bit back on the byte mov es:[di],al ; put 8 bit byte into output inc di ; next output byte loop C7TO8loop2 pop ds pop bp ret 8 ; remove parameters c7to8 endp code ends end