Abstract: A timing vernier applies a pair of stable bias voltages to intermediate points of an impedance string to establish reliable and calibratable delay cell biases for a fine multiplexer. A coarse input multiplexer is switched to a new timing signal substantially immediately after passing a prior valid timing signal to maximize the time prior to each valid output that the waveform is independent of the prior delay pattern. Logic circuitry is provided for three different phase differential regimes between successive timing signals to ensure that invalid output signals separated by less than a clock period are not produced. Mask commands are inserted into a series of timing control commands to equalize the average rates of writing and reading out the timing control commands with the mask commands skipped at readout.