As stated above, you can access the analogs as registers as they come in from the plugin using the register read/write functions. This will let you access a raw ADC or DAC value, usually something along the lines of 0 to 1023 (10 bit ADC/DAC) or 0 to 4095 (12 bit ADC/DAC), etc... Mapping these registers to an analog input give you the capability of working with voltages instead of raw ADC/DAC values, if required.
For example, say you have a 12 bit DAC output with a voltage range of 0 to 10v represented by the scale of 0 to 4095, 0 being 0 volts and 4095 being 10 volts:
Set the numerator to the total voltage swing (0 to 10 = 10 volts total) and the denominator equal to the total capacity of the DAC bits. 12 bits == 4096. Now you can use the mcAnalogOutputWrite() function with volts!
rc = mc.mcAnalogOutputWrite(inst, 1, 7.5) -- Set analog output 1 to 7.5 volts.
rc = mc.mcAnalogOutputWrite(inst, 1, 2) -- Set analog output 1 to 2 volts.
What if you have a bi-polar -10 to +10 volt 12 bit DAC that you want to set?
Set the numerator to the total voltage swing (-10 to +10 = 20 volts total) and the denominator equal to the total capacity of the DAC bits. 12 bits == 4096. Most bi-polar DACs have mid scale as 0 volts, so set the offset to half of the denominator, 2048.
rc = mc.mcAnalogOutputWrite(inst, 1, -10) -- Set analog output 1 to -10 volts. Raw DAC value will be 0.
rc = mc.mcAnalogOutputWrite(inst, 1, 0) -- Set analog output 1 to 0 volts. Raw DAC value will be 2048.
rc = mc.mcAnalogOutputWrite(inst, 1, 10) -- Set analog output 1 to +10 volts. Raw DAC value will be 4096.
Steve