Jon, I guess you just have to 'love' standards huh? heh. Not to give away my age, but the last 'standard' I tried to decipher was NAPLPS.
Now, overlook my ignorance here, please. What boards do you make? Mesa boards? Joe ----- On Apr 23, 2019, at 8:39 PM, Jon Elson el...@pico-systems.com wrote: > On 04/23/2019 11:21 AM, Joe Hildreth wrote: >> Jon, >> >>> I make boards that use the parallel port as a communications >>> channel for motion control. >>> These use the IEEE-1284 (EPP) mode for faster communication. >> How do you test if a card works properly in EPP mode? This would be good >> information to add to the list for those using your hardware. >> >> > All I am concerned with is if it works with my boards. But, > in the process, I learned more than I ever WANTED to know > about EPP. EPP is a horrible "standard", because it really > doesn't seem to be a standard. There is the IEEE-1284 > designation, but I've never seen the standards document, > probably because I can't afford it. The best thing I ever > found was the datasheet from an old ISA-bus multi-IO chip. > Also, there is a Microsoft document that generally lays out > how it is supposed to work. But, chip makers don't follow > any of that. The Microsoft doc shows timing diagrams with > no numbered specs on timing. But, at least, the data bus is > shown as stable before the strobes are asserted. Well, some > chips assert the strobes FIRST, then the data FOLLOWS. Not > even at the same time, but the strobes come 50 ns FIRST! Crazy! > > There was a very old PCI board that failed to hold the CPU > in a wait state, so the strobe would come on and then a > bunch of bytes would be sent rapidly on the data bus. No > WAY to fix that one in software. > > Anyway, one of the areas of confusion is how the data bus > direction is handled. One way is the driver program > commands all direction changes by setting/clearing a bit in > the control register. Another way is the use of INB and > OUTB CPU instructions allows the board to turn the bus > around as needed, automatically. Some boards require the > first way, some require the second, and some will handle > either. So, I had to put in a command line switch on the > hal_ppmc driver to allow the user to select which mode the > driver used. This allowed just about any EPP board to work. > > As for testing, I have a set of public diagnostic programs > on my web site for my boards, and they do communications > reliability testing by sending random data to the board and > then reading it back. > > If I had ONLY KNOWN how big a muddle the EPP was, I likely > would have done something different. > > Jon > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
