David, If you are referring to FPGA type PCI bus boards like the Mesa products, you are not comparing apples to apples when discussing speed. In the case of the parallel port, the base thread which handles the I/O is run on the CPU. In the case of an FPGA board, the base thread is effectively run on the FPGA board. It handles counting of individual pulses from the encoder or generating the pwm or step outputs. The servo thread then just comes around periodically to read the current count, or set a velocity value for the pwms or step generation.
For example, the Mesa 7i43 communicates over the parallel port, but as an FPGA device, it can handle much higher speed counters (encoders), pwms and step generators than the parallel port can by itself. HTH, Eric Hello all, I wanted to say thanks again for all your input and help bringing me up to speed! I'm cranking away researching my Anilam 1100 retrofit, and I'm having troubles feeling secure about the parallel port as a robust enough device to control three or four axis of motion at modest 100ipm table speeds. I can see a PCI based I/O card doing it, but I'm feeling iffy about the parallel port. I know that EMC is super competent using either style device for it's main motion control I/O. The two axis Anilam 1100 machine I have now has a program/DRO resolution of 0.0001", and can machine up to 100ipm. I would like to retain these performance parameters after the retrofit at a minimum if possible. I think I read somewhere that EMC can control up to 8 axis (or more) of motion through the parallel port. What I'm concerned with is, how fast can it control motion compared to a PCI based I/O device. I read (I tried to anyway) a white paper on the specifications of the ISA parallel port standard. It really is not that fast of a device compared to the PCI bus standard. Well, it seemed that way to me. I'm looking to make this retrofit as reliable as possible, and get some decent performance out of it to. Is there a point in which the parallel port is not fast enough, or not a wide enough data pipe to do the job? Or is it fast enough for anything an automated machine tool would ever need? Parallel port? PCI I/O card as a port? Red pill? Blue pill? ;-) Sorry if this has been asked before: Are there any main stream commercial machine tool companies out there that use the PC's parallel port device for motion control? Companies like Haas, Mazak, Harding, Bridgeport, Hurco, Monarc, etc? ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
