On Sun, 24 Jun 2018 12:34:19 -0700 Chris Albertson <albertson.ch...@gmail.com> wrote:
> Your buffer reading example is, I think a better example of soft real > time. Typically the way this is done is not to trigger on "buffer full" > but use a 70% threshold. My definition of "soft" means that it must be > fast enough to get the work done but there is some room for when each part > of the job needs to get done For serial receive there is a hard limit unless data is to some degree useful even though it is partly corrupted. Soft limit is whenever result is not totally useless if dead line is missed which usually is the case for serial receive but if data could be resent in time it turn into a soft limit. > "Hard" usesusaly has a numeric duration or rate requirement with a "small" > tolerance. "Small is kind of imprecise and could be anything from > milliseconds to nanoseconds. For serial receive data is overwritten or new data missed with a very small tolerance and even though it may take some time for all data in buffer to be overwritten a single bit overwritten in a message usually make it useless because of CRC value will be wrong. > A good example of a hard real time requirement is closer to what we do > here -- motion control. But also run a PID loop at 100 Hz or maybe to > output analog signal at 48,000 samples per second to synthesize some > waveform you need. Motion control certainly is a good example because it is totally useless to calculate then output should change then it already have changed. > What we have is the result of historic accident. EMC and machine control > in general got its start when computers where EXPENSIVE. ... In the last few years very cheap and very good micro controllers more or less made for machine control have become avaible. A few years ago development tools for software where expensive while it is now available for free. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
