Question:
DC motor (fig 1) is operated through
two terminals, whenever the potential difference is created (through batteries,
cells etc) across these terminals the motor starts its motion.
Suppose we have connected a DC
motor to our system’s parallel port through a secure circuitry (fig 3).
We wish to operate the DC motor
through our parallel port (fig 2) using some input through our keyboard. Like
“F” key for running motor in “Forward Direction”, “R” for “Reverse Direction”,
“S” for “Stop” and “E” for “Exit from code”.
We have suggested that we will
use parallel port’s Pin 2 and Pin 3 (the last 2 pins of parallel port’s data
check fig 2 and table 1).
|
Pin 2
|
Pin 3
|
Outcome
|
|
0
|
0
|
Stop
|
|
0
|
1
|
Forward
|
|
1
|
0
|
Reverse
|
|
1
|
1
|
No Operation
|
Table 1
You have to write a code in assembly language that take an input
character from keyboard (S, F, R and E) and on the basis of these characters
transmit the code (with respect to the truth table) to the parallel port to
operate that connected DC motor.
