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Assembly Source File  |  1986-03-11  |  2KB  |  64 lines
  1.         PAGE        ,132
  2.  
  3. ; --    absread -- absolute track and sector read
  4. ;       Version 1.1     December 30, 1985
  5. ;       Glenn F. Roberts
  6. ;       calling convention:
  7. ;              absread(drive, nsect, sector, &buffer);
  8. ;       where:
  9. ;              drive = drive no. (A=0, B=1 ... )
  10. ;              nsect = number of sectors to read
  11. ;              sector = beginning logical sector number
  12. ;              buffer = array to hold data
  13. ;       returns:
  14. ;              0        Normal return, no error
  15. ;              1        Write protect violation
  16. ;              2        Unknown unit
  17. ;              3        Drive not ready
  18. ;              4        Unknown command
  19. ;              5        CRC error
  20. ;              6        Bad drive request structure length
  21. ;              7        Seek error
  22. ;              8        Unknown media
  23. ;              9        Sector not found
  24. ;              10       Printer out of paper
  25. ;              11       Write fault
  26. ;              12       Read fault
  27. ;              13       General disk failure
  28.  
  29. _text   SEGMENT BYTE PUBLIC 'CODE'
  30.         ASSUME  CS:_text
  31.  
  32.         PUBLIC  _absread
  33.  
  34. _absread PROC   NEAR
  35.         PUSH    BP              ; set up stack addressing
  36.         MOV     BP,SP
  37.         PUSH    DI
  38.         PUSH    SI
  39.  
  40.         MOV     AX,[BP+4]       ; AX = drive number
  41.         MOV     CX,[BP+6]       ; CX = number of sectors
  42.         MOV     DX,[BP+8]       ; DX = starting record
  43.         MOV     BX,[BP+10]      ; DS:BX = buffer address
  44.  
  45.         INT     025H            ; request absolute read
  46.         INC     SP
  47.         INC     SP              ; fix the stack
  48.  
  49.         JC      ERROR           ; if error then return code
  50.         XOR     AX,AX           ; else show normal return = 0
  51.         JMP     SHORT DONE      ; and then exit
  52.  
  53. ERROR:  MOV     AH,0            ; error - zero high byte
  54.         INC     AL              ; and increment error no.
  55.  
  56. DONE:   POP     SI              ; restore registers
  57.         POP     DI
  58.         POP     BP
  59.         RET                     ; and return
  60. _absread ENDP
  61.  
  62. _text   ENDS
  63.         END
  64.