The output of device A is able to drive the input of device B provided that all these conditions are met:
VOL (max) of A is ≤ VIL (max) of B
VOH (min) of A is ≥ VIH (min) of B
IOH (max) of A is ≥ IIH (max) of B
IOL (max) of A is ≥ IIL (max) of B

Can anyone explain or provide me with a suitable link?
I only do not understand the first condition

 

The first condition?

Unless the maximum possible low output value of A is always less than the permissible low input range of B, then A's output cannot be guaranteed to always drive B's input to the valid low state.

 

Perhaps I could have more correctly stated the relevant part of the sentence as :-

"... always no greater than the permissible low input range ..."

- so as to better match the "less than or equal to" condition.

Finding the words is never easy! I'll keep trying.

 

errr I prefer a digram. where does the current flow?

 

errr I prefer a digram. where does the current flow?

The first and second statements are valid even if no current flows. All four are general requirements for any voltage-mode logic system - TTL, CMOS, ECL.