On 16.12.15 10:37, andy pugh wrote: <snip great stuff, filed for reference.>
> LUT5 is extremely useful. It allows you to set up a single output for > any combination of up to 5 inputs. Great for things like machine > guards, pneumatic chuck releases etc. (door must be open, spindle must > not be turning, switch or pedal pressed, for example). > It gets even more useful of you connect the output back into an input. > Then it can have different behaviour depending on current state. Ooh, from that, if the feedback is anded with a couple of inputs, then an RS flip-flop can be formed, providing memory of a transient condition. (I'm tentatively imagining a tool carousel, and the LUT5 remembering "we're turning CW" or "we've passed the Home index", etc. Grab a handful of LUT5s, and who needs Classic Ladder for a micro-PLC job? (Sorry, couldn't resist getting carried away.) > I wanted my PSU to be allowed to turn on as long as the bus voltage > was low and to be able to turn off under any conditions. I did this be > feeding the machine-on, bus-high, bus-low an current output into 4 > inputs, then spent a little while looking at the truth-table in my > LUT5 tool. Ah, you've already done it. If the output is "PSU On", then ISTM you're defining a latch with gated Set conditions, and an unconditional Reset input? The LUT5 then replaces a whole fistful of ANDs & ORs (or NANDs & NORs, as we'd do in hardware.), two already in the latch, plus whatever input gating is performed. > At the moment it behaves the same regardless of the bus-high input, > but it is one hex number to change to alter that. > http://linuxcnc.org/docs/2.7/html/man/man9/lut5.9.html > and the online LUT5 tool > https://docs.google.com/spreadsheets/d/1_VlL39jUOPpS8Tt9mpRK-eaSTS6C6PHBDoE3JitvLzs/edit?usp=sharing The ability to define the entire logic behaviour with a single Int is just mind-bogglingly elegant. (Even if a little mind-warping the first time a configuration is attempted. :) Thank you for the food for thought. Erik It was 36°C (97°F) in the shade mid-morning when I ventured out to rid the spouting of flammables, after sweeping leaves & sticks off the roof yesterday. Heading for 40+ and thunderstorms on the weekend. Could be fires. (A bit early, but they did make a small start in Spring, already.) Could be a long summer. ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
