Over the years, it has been seen that certain parallel port chips did not work properly with my hal_ppmc driver. Some of these chips were just admittedly broken in EPP mode. It all seemed to settle down by 2010 or so, and I thought the bad chips were a thing of the past. I recommended SIIG PCI cards with Oxford chips, and all was good. Then, I found that, to my horror, SIIG PCIe cards did not work! That was a confusing nightmare, to tell people to get SIIG PCI cards, but avoid their PCIe cards. I did identify ***ONE*** PCIe chip that worked. Not good to be sole-source.
Kumar Bhatia of Axxon in Canada had communicated with me a long time ago about making their own industrial-grade parport cards. He apparently is also involved in qualifying other cards for industrial use and is very up on EPP mode. I sent him a text description of the sequence of inb/outb commands that my driver used, and what (incorrect) behavior the EPP card gave. He noticed that all the newer chips do NOT require the program to switch the parport bus direction, the read or write request to the PCI register does it automatically. Well, I tried this on my diagnostic, and it WORKS! So, at least on the Siig card with the OXPCIe952 chip, this switching of the direction in the control register actually BREAKS the EPP read operation. I have one other PCIe card and some PCI cards that are known to not work, I will test the rest of those this weekend to see if the same interference is the cause. Now, in the long distant past of ISA-bus multi-IO chips and maybe some early PCI parport chips, the program DID have to change the bus direction bit in the control register when switching between read and write operations on the EPP bus. So, my hal_ppmc driver does this, and it works on a number of PCI chips, both of the on-motherboard and plug-in card type. It also works fine on MCS9900 and MCS9901 chips. So, now, the quandary is what to do with the hal_ppmc driver? If I take this command out of the driver, it will only affect new versions. Are all the parport chips that NEED the "manual" direction changing so far back in history that nobody could ever run a current LinuxCNC on those motherboards and parport cards? Any comments will be very welcome! Jon ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
