How the MACRO Electronics Works

The MACRO electronics use a circular buffer (WFD) with zero suppression. There is a threshold, if the input is above this threshold it writes the ADC value and the time. The trigger issues the MACRO electronics Start and Stop commands. When it gets a Stop it stops the buffer and an interrupt gets sent to the DAQ. Depending on the type of interrupt the DAQ then reads out the buffer for some fixed amount of time before the Stop. Once it is finished reading a Start command is issued.

There is an added complication that there is only one circular buffer for 4 channels (only 2 or 3 are connected since we have enough boards). The buffer records the total voltage, and which of the 4 channels were above threshold, sometimes this could be more than one channel in which case you can only tell the total voltage. (This is after the summing of 6 PMTs to one MACRO input in the LBL electronics, meaning 12 or 18 PMTs per MACRO waveform.)

The readout time for the short stop is 150us and 1ms for the long stop.