Atari XL User Manual

186 The Atari XL Handbook
registers depending on whether data is being read
or written.
It is not possible to clear the collision detection
registers by wri ting zeros to them. The registers
are cleared by POKEing to a special address called
HITCLR, at 53278. It does not matter what value
you write this location, the effect is to clear all
sixteen collision registers.
The final example programs demonstrate the
detection of collisions between players, and
between a player and an object on the display. The
first program demonstrates the detection of
collisions between two players.
10
20
30
40
50
60
70
80
Note:
REM PLAYER-PLAYER COLLISIONS
POKE 53261, 255: POKE 704, 87
POKE 53262, 255: POKE 705, 55
FOR X=O TO 255
POKE53248, X: POKE 53249, 255-
X
IF PEEK(53260)=2 THEN PRINT
"{BELL}"
POKE 53278, 0
NEXT X
The (BELL' character is CONTROL-2
The second program shows the detection of
collisions between a player and a coloured
rectangle drawn on the mode 5 display.
10 REM PLAYER-DISPLAY COLLISIONS
20 GRAPHICS 5
30 POKE 53261, 255: POKE 704, 87
40 COLOR 1: PLOT 30, 30:
50 DRAWTO 30, 10: DRAWTO 20, 10:
60 POSITION 20, 30: POKE 765, 1:
70 XIO 18, #6, 0, 0, "S:"

Atari XL Specifications

General

Release Year	1983
CPU	MOS Technology 6502C
Graphics	ANTIC, GTIA
Sound	POKEY (4 channels)
Storage	Cassette tape
Ports	Cartridge
Operating System	Atari BASIC
CPU Speed	1.79 MHz
RAM	64 KB