Sem 5‎ > ‎CA LAB‎ > ‎

03 Setting the Digital Clocks

posted Nov 4, 2012, 1:37 AM by Neil Mathew

The DigiClocks can be found in the SOURCE Library.

I've classified them in the ways I've used them. 
This may not be the conventional method, but it works for me.

My Type #1: Normal Varying Clock Signal (INPUT)
OFFTIME- duration of low (0)
ONTIME- duration of high (1)

These control the duration of the high and low cycles of the clock.
Both are set equal at 0.2uS so that they are high and low for equal durations.

When there are many clock inputs required, inorder to see my output clearly, 
I keep each clock with a different duration, usually in multiples.
eg: 0.1uS , 0.2uS , 0.4uS , 0.8S

STARTVAL - the starting value of the clock
Here, set as 0.

My Type #2: Fixed Value Clock Signal (ENABLE)

Here, I alter the OFFTIME and ONTIME by assigning one of them a value of 0uS

That way, it will remain in only one state: low or high.

Always 0:

Always 1:


Notice how the STARTVAL does not matter here.

My Type #3Changing the Delay

In order to distinguish between the various input clock signals, I initially used delay instead of changing the ontime and offtime. They used to create excessive propagation delays which I found unfavorable.

Hence, I don't use this type anymore.