I am using a L293D motor driver with arduino uno r3. Just wanted to know whether I can give pwm signals on Enable pins or not.
I always thought so, but this thread at Stackexchange says you should PWM the A pins not the EN pins.
Figure 1 in the 293 datasheet shows a pulse on pin A not EN, although I don't see where it says you can't.
That depends on what you want the motor to do during the off period. If you leave the EN pin HIGH and pulse the A pin, the motor will "fast stop" (brake) during the off period. If you pulse the EN pin, the motor will "slow stop" (coast) during the off period.
The logic chart on the datasheet seems to be in error. With the EN pin LOW, the motor will "slow stop" (coast). http://www.ti.com/lit/ds/symlink/l293.pdf