titus-larsen-titus-1981-apple-interfacing

LED
BIT
RED } D3
YELLOW EL M D4
GRE EN D 5
LED
RED }
YELLOW
GRE EN
MAIN
.
You must now determine the patterns of logic ones and zeros that
required to turn the individual LEDs on or off. In our circuit,
latch chips were used to drive the LEDs directly, and a zero
ed a LED on, while a one turned a LED off. What values are
u going to use to turn the various LEDs on and off
e found that the following binary values were needed. The deci­
. equivalents have also been provided for you.
Red 254 11111110
Yellow 253 11111101
Green 251 11111011
MAIN Red 247 11110111
MAIN Yellow 239 11101111
MAIN Green 223 11011111
To start the traffic-light control operation, write a program that
'II flash the yellow light on Main Street and the red light on Elm
reet; one second on and one second off. What is the "on" pattern,
d what is the "off' pattern
e off pattern is 255, or all logic ones, while the on pattern has
ts D4 and DO both as logic zeros, or 23810• We used the following
POKE 49318,255
FOR T = 0 TO 770: NEXT T
POKE 49318,238
FOR T = 0 TO 770: NEXT T
GOTO 10
137