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  1. .PAGE 'IRQ'
  2. ;
  3. ;
  4. ;
  5. SYSIRQ PHA ; SAVE .A,.X,.Y
  6. TXA
  7. PHA
  8. TYA
  9. PHA
  10. ;
  11. ;
  12. LDA IFR1 ; TEST IF ATN
  13. AND #2
  14. BEQ IRQ10 ; NOT ATN
  15. ;
  16. JSR ATNIRQ ; HANDLE ATN REQUEST
  17. ;
  18. ;
  19. IRQ10 LDA IFR2 ; TEST IF TIMER
  20. ASL A
  21. BPL IRQ20 ; NOT TIMER
  22. ;
  23. JSR LCC ; GOTO CONTROLLER
  24. ;
  25. IRQ20 PLA ; RESTORE .Y,.X,.A
  26. TAY
  27. PLA
  28. TAX
  29. PLA
  30. RTI
  31. ;
  32. ;
  33. ;
  34. .END