emc servo question

I have a simple question about EMC and how it controls servos. Let's say I
have a way to get encoder signals into EMC. EMC does some calculations and
comes up with a number that is outputted to a D/A converter. This D/A
sends a voltage to drive a servo amp. Is this voltage simply amplified and
is proportional to the voltage sent to the servo motor, or is it
proportional to the current sent to the servo motor? How many bits is it
usually? I think the Geckos are internally 8 bits.

Thanks,

Steven Ciciora