Well...it appears there are issues with some of the generic devices.
Using the EXOR you used in a compound configuration, I was able to achieve the proper results for my circuit. Its a bit messy as I just Kludged the 5 Input EXOR equivalent into my circuit.
In any case it is working wonderfully.
I attached the circuit...feel free to use/abuse...
I built the circuit to simulate control of a Maxim digital potentiometer using an Optical Encoder control. The Optical Encoder provides a 2 wire quadrature output. It could be used with any compatible gray code counter; however, the Maxim pot contains its own up/down counter. Its interface uses an up/down control, when held High the wiper position will increment and decrement when held low with a clock input on another pin.
I used two digital inputs with one delayed by .25 msec to emulate the output of the Optical Encoder. This is input into a D Flip Flop to detect rotational direction. If CW, the first output of the Encoder will lead the second output by 90 degrees and opposite for CCW rotation. Since the counter in the Maxim Pot could overflow (restart at zero) if CW rotation passed its max count and it could also overflow if rotated CCW past zero, I needed a way to stop up or down count if either min or max was reached. Further, I needed that control to recognize during max count that a decrement command was present and allow it to count down. The same is true if min count is reached. So, if the user rotates CW beyond max count, the count stops at max and only reacts to a down count or CCW rotation. The same is true if the user trys to rotate CCW beyond min count.
The only step left is to build in enough counters to count to the potentiometers max count.
