A method and apparatus in a DC-feed controller for controlling a subscriber line
interface circuit controlling voltage (alternately, current) on a telephone line
comprising a pair of wires. A digital feedback signal is subtracted from a predetermined
voltage (alternately, current) limit digital value to provide a digital error signal
that represents the difference between the voltage (alternately, current) limit
digital value and the digital feedback signal. The digital error signal is multiplied
by a predetermined digital gain value to provide a scaled digital error value.
The scaled digital error value is integrated over time to generate an integrated
digital error signal having a first predetermined number n of significant bits.
A modified digital error signal is received, comprising a second predetermined
number m of bits, where m
