The Synthesis: Combining All 68 Lessons

This final project demonstrates how to structure and link together all the advanced modules developed in this series (Interrupts, Graphics, I/O, and Logic) to create a working, real-time application.

The Engine’s Goal: Display a sprite that moves smoothly in response to keyboard input, accelerates due to gravity, and stops when hitting a floor tile.

Engine Initialization (The Setup Phase)

This phase runs only once, at boot, and relies heavily on your OS and peripheral posts (Parts 52, 62).

The Setup Sequence:

INIT_SYSTEM:
    DI                     ; Disable Interrupts (Part 48)
    LD   SP, STACK_TOP     ; Initialize Stack (Part 52)
    
    CALL INIT_MEMORY_BANKS ; Configure RAM/ROM (Part 43)
    CALL INIT_VIDEO        ; Clear screen (Part 21)
    CALL INIT_CTC_TIMER    ; Set up VSync Timer Interrupt (Part 62)
    CALL INIT_SPRITE_DATA  ; Set initial X, Y, and velocity (Part 31)

    IM   2                 ; Set Interrupt Mode 2 (Part 60)
    EI                     ; Enable Interrupts (Part 48)
    RET

The Main Game Loop Structure

The main loop runs infinitely, synchronizing all actions to the V-Blank Interrupt (VBI) for smooth animation (Part 25).

GAME_MAIN_LOOP:
    CALL CHECK_KEYBOARD    ; Check the FIFO buffer (Part 58)
    CALL UPDATE_LOGIC      ; Apply physics/gravity (Part 34)
    
    HALT                   ; Wait for the next VBI interrupt (Part 25)
    
    CALL RENDER_SPRITES    ; Draw/erase sprites (Part 32)
    
    JP   GAME_MAIN_LOOP     ; Loop infinitely

The VBI Interrupt Service Routine (The Scheduler)

The VBI is the real heart of the game, forcing the execution of critical physics and rendering updates.

The ISR (Simplified):

VBI_ISR_HANDLER:
    PUSH AF, HL            ; Save necessary context (Part 47)
    
    CALL PHYSICS_ROUTINE   ; Updates sprite velocity/position
    CALL COLLISION_ROUTINE ; Check if the new position is solid (Part 37)
    CALL RESOLUTION_ROUTINE; If collision, backtrack/stop (Part 35)

    POP  HL, AF
    RETI                   ; Return from Interrupt (Part 48)

Final Conclusion

This engine represents the fusion of the entire curriculum:

  • Low-Level Control from I/O ports and interrupt vectors.
  • Data Structures from the sprite descriptors and linked lists.
  • Algorithms from the multiplication, shifts, and physics routines.

Congratulations on completing the most comprehensive Z80 Assembly curriculum!