Collisions#

The TIA detects collisions in hardware. As the beam draws each scanline, the chip notices whenever two objects are lit at the same pixel and latches a bit. You never compute overlaps yourself — and given how little of the 76-cycle line you’d have to spare for it, that’s a gift. Your part is just to read the latches after the frame and clear them before the next.

That free, pixel-perfect detection is what turns the playfield and the movable objects into a game: the ball meets the wall, the missile meets the tank, the player meets the maze.

  • The Collision Registers — the six objects, the 15 pairs, and the eight registers that report them (with a lookup matrix).
  • Reading & Clearing — the BIT/N–V idiom for testing a latch, and the once-a-frame CXCLR discipline.

Collisions accumulate until cleared. Forgetting the CXCLR write each frame is a classic bug: a single touch appears to last forever.

Backward Sprite Multiplexing The Collision Registers Forward