How the LBL Electronics Works

The LBL electronics has two waveform digitizers (ATWD) connected to each PMT labeled A and B. A waveform is storded on ATWD A & B ulternately if the input signal goes above a programmable threshold (currently set at ~1/3 photo electron). The waveforms are 128 samples long (which corresponds to ~200ns). Each waveform is stored on the ATWD for a programmable length of time after sampling (currently set at 175ns) if a global trigger command (see table) is not received in this time the waveform is overwritten.

Aside from the global trigger there are many other 5 bit trigger commands that can be sent to the LBL electronics, see table below.

The inner detector (ID) crates (numbers 1 to 5 & 7 to 10) and outer detector (OD) crate (number 6) can receive different trigger commands.

Table: Trigger commands as sent by the trigger and recorded by the LBL electronics.

Command (Hex) Function
1 Global acquisition
2 Forced acquisition, ATWD A highest gain
3 Forced acquisition, ATWD B highest gain
4 Acquire 40MHz CLK, ATWD A
5 Acquire 40MHz CLK, ATWD B
6 Reset timestamp timer
7 Forced acquisition, no priority
8 Testpulser, ATWD A
9 Testpulser, ATWD B
a Testpulser, ATWD A, forced acquisition
b Testpulser, ATWD B, forced acquisition
c Testpulser, no acquisition implied
12 Forced acquisition ATWD A all 3 gain
13 Forced acquisition ATWD B all 3 gain
1d Reset FPGA
1e Increment testpulser enable