Is my understanding Digital devices all screwy, i'm talking about their datasheets?

Question

How do you figure out what a digital gate senses as HIGH and LOW? I
thought it was labeld VIH, VIL, VOH, and VOL. But ive been told that by
setting VIH you can set what VOH is. Totally confused by this. I
thought there was a specified range, and that was what you used.
According to other people you could, "set", and have a VIH at 1 Volt.
How do these setting really work?

I am talking about regular digital devices, like 4011. I am not talking about PICs or anything that is computer programmable.

Hossein, that was exactly my understanding. However someone told me that it all depend on the relationships betten the Ins and Outs, which basically makes no sense what-so-ever.

Answer 1

I am confused. What is a digital devices ?
Would you name a manufacturer and it's part number ?

Answer 2

there is a threshold for High and Low for digital gates. for instance: (between 0 and 2 volts will be 0) and (between 3 and 5 volts will be 1).
if these threshold is not suitable for you, you can use some resistors to obtain the right values.

Answer 3

I am not aware of any "setting" of VOH in TTL or CMOS devices. They are usually spec'd as minimum and maximum input/output levels. Some devices (CMOS) will work at a range of power voltage levels, and their input/output thresholds will vary accordingly, but in all my experience, output and input are fully isolated. Who are these people who are telling you this? Make them back up their statements with data sheets.

Answer 4

Order the data book for the chip from the manufacturer. It has all the specifications and definitions.