An apparatus comprising a write circuit, a processing circuit and a monitor circuit. The write circuit may be configured to generate one or more write control signals in response to an input signal. The processing circuit may be configured to generate an intermediate control signal in response to (i) the input signal, (ii) a reference clock signal and (iii) one or more user input signals. The monitor circuit may be configured to generate a sample signal in response to (i) the write control signals and (ii) the intermediate signal. The sample signal may represent a waveshape of the write control signals used to monitor writing to a data storage system.