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Text File  |  2000-06-30  |  896b  |  36 lines
  1.  
  2. ;**    DEF8253 - 8253 PROGRAMMABLE INTERVAL TIMER DEFINITIONS
  3. ;
  4.  
  5. ;  PORT DISPLACEMENTS
  6.  
  7. PITC0    EQU    000H        ;COUNTER 0
  8. PITC1    EQU    001H        ;COUNTER 1
  9. PITC2    EQU    002H        ;COUNTER 2
  10. PITCW    EQU    003H        ;CONTROL WORD
  11.  
  12. ;  CONTROL WORD
  13.  
  14. PITSC    EQU    11000000B    ;SELECT COUNTER
  15. PITSC0    EQU    000H        ; 0
  16. PITSC1    EQU    040H        ; 1
  17. PITSC2    EQU    080H        ; 2
  18.  
  19. PITRL    EQU    00110000B    ;READ/LOAD
  20. PITRLCL    EQU    000H        ; COUNTER LATCHING OPERATION
  21. PITRLMB    EQU    010H        ; MSB
  22. PITRLLB    EQU    020H        ; LSB
  23. PITRLW    EQU    030H        ; WORD
  24.  
  25. PITM    EQU    00001110B    ;MODE
  26. PITMITC    EQU    000H        ; 0 - INTERRUPT ON TERMINAL COUNT
  27. PITMP1S    EQU    002H        ; 1 - PROGRAMMABLE ONE SHOT
  28. PITMRG    EQU    004H        ; 2 - RATE GENERATOR
  29. PITMSW    EQU    006H        ; 3 - SQUARE WAVE RATE GENERATOR
  30. PITMSTS    EQU    008H        ; 4 - SOFTWARE TRIGGERED STROBE
  31. PITMHTS    EQU    00AH        ; 5 - HARDWARE TRIGGERED STROBE
  32.  
  33. PITBCD    EQU    00000001B    ;0 = 16 BIT BINARY COUNTER
  34.                 ;1 = 4 DIGIT BCD COUNTER
  35.  
  36.