The TIA (as seen by the programmer)
10.0 Collisions
The TIA detects collisions between any of the 6 objects it
generates (the playfield and 5 moveable objects). There
are 15 possible two-object collisions which are stored in
15 one bit latches. Each collision register contains two
of these latches which are read by the microprocessor on D6
and D7 of the data bus for easy access. A "1" on the data
line indicates the collision it records has occurred. The
collision registers could be read at any time but is
usually done during vertical blank after all possible
collisions have occurred. The collision registers are all
reset simultaneously by writing to the collision reset
register (CXCLR).