deanr@sco.COM (Dean Reece) (03/14/90)
In article <1745@xn.LL.MIT.EDU> tj@XN.LL.MIT.EDU (Thomas E. Jones) writes: ... >Output A ----- ----- ----- ----- > | | | | | | | | > ---- ----- ----- ----- ----- > >Output B ----- ----- ----- ----- > | | | | | | | | > ____ _____ _____ _____ _____ > >Clockwise, time scale increases going right/left. >Counter clockwise, time scale increases going left/right. > >I need to convert this signal to 2 digital lines that would control a standard >TTL up/down counter. Standard TTL counters have an U/D' (up, down) signal and >a clock (count) signal. I remember seeing very simple circuits to do this, >perhaps just a few gates and a few F/F's, but I can't find it. This is easy. I used a similar encoding technique on a trac-ball once: Every time B is rising while the shaft is rotating CW, A will be high. Every time B is rising while the shaft is rotating CCW, A will be low. So if you used an Edge triggered Counter and let B be the Clock signal and A be direction, it will just work. For that matter, it doesn't matter if the counter you use has a positive or negative edge triggered clock. All you need to do is swap the A and B signals to reverse the direction of count relative to the direction of shaft rotation. Hope it helps --- have fun ______________________________________________________________________ | Dean Reece Member Technical Staff |"The flames are all long gone | | The Santa Cruz Operation 408/458-1422 | but the pain lingers on" | |___________deanr@sco.com_______________|___________________Pink_Floyd_|