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  1. joshdoe

    ADC saturating for no apparent reason

    The problems with my DAQ never seem to end. I've got an Apex Stratus X ND ADC and an RTD DM6620 DAC in a PC104 system. The DAC creates a 15kHz 1000-step triangle wave that provides modulation to an RF generator in an NMR system. The NMR signal goes through an amplifier, and then to the ADC...
  2. joshdoe

    Configuring all three counters on a 8254 chip

    itsmoked: Thanks for the suggestion. I have programmed Atmel AVR's before, and even considered using one in this system. It would be very elegant, which I would love. However, there are a few concerns keeping me back. One is the ease of making changes in the future. I won't always be around, so...
  3. joshdoe

    Configuring all three counters on a 8254 chip

    itsmoked: Thanks for all the info. I've now got counter 1's GATE pulsed low right after I write the new count value. My meter-counter seems like it might be a little flaky, so now I'm using another 8254 on the DAC card which counts the pulses, and an ADC (which also has an 8254) being...
  4. joshdoe

    Configuring all three counters on a 8254 chip

    felixc: I'm using a 25MHz counter (nuclear equipment) to count the pulses and a digital o scope. With and without the feedback counter 0 produces the expected frequency correctly. designchain: It may be ancient, but it seems to work very well for my purposes, except for the current problem...
  5. joshdoe

    Configuring all three counters on a 8254 chip

    IRstuff: the 8254 counter is actually rated for 10MHz, but the DAC card which this is built into provides an 8MHz clock.
  6. joshdoe

    Configuring all three counters on a 8254 chip

    Thanks itsmoked, not solved yet. I thought it might be a problem with speed, but it doesn't matter whether I have the first timer going at 15kHz, 1kHz, or 1MHz.
  7. joshdoe

    Configuring all three counters on a 8254 chip

    I've made some headway. I've now got it so that it reliably spits out pulses in multiples of 1 000, just not the number I want, i.e. I say 200 000, but i get between 150 000 and 195 000. So it seems like counter 2 is being decremented too quickly.
  8. joshdoe

    Configuring all three counters on a 8254 chip

    I've got an 8254 timer/counter chip that is part of a DAQ system. What I want to do is generate a 15kHz signal, but have it put out only a very precise number of pulses, in a range from 100,000 to 2,000,000. However, I am getting a wide range of pulses, so when I ask for 200,000, instead I get...

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