Stephan, can you give us a clue what it is all about? What happens with the data after being decoded by the FPGA?
Best regards Ulrich Bangert > -----Ursprungliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von Stephan Sandenbergh > Gesendet: Mittwoch, 19. November 2008 15:30 > An: Discussion of precise time and frequency measurement > Betreff: [time-nuts] M12+T ASCII interface - I'm confused? > > > Hi All, > > Up until now we've been interfacing my Motorola M12+T's using > the Oncore software. However, at this point we are trying to > have it interfaced directly to a FPGA. To my mind this should > be simple - the commands are discriminated (framed) by > looking at the start and terminating bytes sequences when > they enter the FIFO, check summed, decoded etc. > > However, I noted something very peculiar about the motorola > ASCII protocol: The start bytes @@ and he terminating byte > <CR><LF> aren't unique with respect to the data bytes. For > instance one could receive a time of 13hrs and 10mins which > would look identical to the terminating characters. Initially > I thought it made sense since the data is also sent in ascii > format. It appears not to be the case. > > It seems to me that the only way in which a command could be > robustly identified and check summed is when the interface > knows the length of the expected return. Obviously, the data > lengths are dependent on both the actual command and the > specific request. This type of intelligence is cumbersome to > implement in FPGAs. > > It would be of great help if you could point me in the right > direction here. I feel rather stupid in asking such a simple > question, but at this point I can't seem to see the light. > I'm flabbergasted... > > Best regards, > > Stephan > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > and > follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.