TIA 1A - TELEVISION INTERFACE ADAPTOR (MODEL 1A)
7. Collision Detection Latches
The serial outputs from all the graphics registers
represent real time horizontal location of objects on the
television screen. If any of these outputs occur at the
same time, they will overlap (collide) on the screen.
There are six objects generated on this chip (five moving
and playfield) allowing fifteen possible two object
collisions. These overlaps (collisions) are detected by
fifteen "and" gates whenever they occur, and are stored in
fifteen individual latch register bits, as shown in figure
The microprocessor can read these fifteen collision bits on
data lines 6 and 7 by addressing them two at a time. This
could be done at any time but is usually done between
frames (during vertical blank) after all possible
collisions have serially occurred.
All collision bits are reset simultaneously by the
microprocessor using the reset address CXCLR. This is
usually done near the end of vertical blank, after
collisions have been tested.