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- | ====== Trigger ====== | ||
The main purpose of the trigger is to implement a coincidence between the S800 focal-plane fast timing scintillator [[Detectors# | The main purpose of the trigger is to implement a coincidence between the S800 focal-plane fast timing scintillator [[Detectors# | ||
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- | ===== Trigger Schematic ===== | + | ====== Trigger Schematic ====== |
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The trigger schematic is shown on the Graphical User Interface (GUI) displayed in the figure below. | The trigger schematic is shown on the Graphical User Interface (GUI) displayed in the figure below. | ||
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- | ==== Trigger Box ==== | + | ===== Trigger Box ===== |
In addition to the singles and coincidence triggers, two separate trigger sources labeled " | In addition to the singles and coincidence triggers, two separate trigger sources labeled " | ||
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- | ==== Gate generation ==== | + | ===== Gate generation |
All digitizer gates and start signals are derived from the live trigger signal, with the exception of the QDC gate which is directly generated from the S800 source signal. The reason is to avoid long analog delays on the scintillator signals. A fast clear circuit is provided to clear the QDC if no valid trigger was generated. | All digitizer gates and start signals are derived from the live trigger signal, with the exception of the QDC gate which is directly generated from the S800 source signal. The reason is to avoid long analog delays on the scintillator signals. A fast clear circuit is provided to clear the QDC if no valid trigger was generated. | ||
- | ==== Inspect channels ==== | + | ===== Inspect channels |
A set of four inspect channels are patched out to the Data-U6 panels. Each channel can be assigned to any connection drawn on the GUI, thereby providing a convenient way to diagnose and adjust the timings at each step of the trigger circuit. | A set of four inspect channels are patched out to the Data-U6 panels. Each channel can be assigned to any connection drawn on the GUI, thereby providing a convenient way to diagnose and adjust the timings at each step of the trigger circuit. | ||
- | ==== Busy Circuit ==== | + | ===== Busy Circuit |
As each controller and external data acquisition perform their readout sequence in parallel, they have different busy times. The busy circuit following the generation of raw triggers is mainly composed of a latch that is set by the "Raw trigger" | As each controller and external data acquisition perform their readout sequence in parallel, they have different busy times. The busy circuit following the generation of raw triggers is mainly composed of a latch that is set by the "Raw trigger" | ||
- | ==== Time Stamping Scheme ==== | + | ===== Time Stamping Scheme |
Because the USB-based S800 data acquisition uses independent crate controllers that perform the readout in parallel, time stamping and busy schemes are incorporated in the trigger to synchronize events and insure no trigger is generated while readout sequences are being executed. Because of this modularity, adding an external data acquisition system (typically from an external detector), is straightforward. More details about the time stamping can be found [[Trigger# | Because the USB-based S800 data acquisition uses independent crate controllers that perform the readout in parallel, time stamping and busy schemes are incorporated in the trigger to synchronize events and insure no trigger is generated while readout sequences are being executed. Because of this modularity, adding an external data acquisition system (typically from an external detector), is straightforward. More details about the time stamping can be found [[Trigger# | ||
- | ===== Trigger module ===== | + | ====== Trigger module |
The S800 trigger logic is built in a LeCroy ULM2367 FPGA module. Note that this module could be replaced in the future by another FPGA module provided it has enough NIM or ECL input/ | The S800 trigger logic is built in a LeCroy ULM2367 FPGA module. Note that this module could be replaced in the future by another FPGA module provided it has enough NIM or ECL input/ | ||
- | ==== CAMAC commands ==== | + | ===== CAMAC commands |
The following table lists the CAMAC codes recognized by the trigger module and their signification. | The following table lists the CAMAC codes recognized by the trigger module and their signification. | ||
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- | ==== Inputs and outputs ==== | + | ===== Inputs and outputs |
The following table lists the inputs and outputs to/from the trigger module and their assignment. | The following table lists the inputs and outputs to/from the trigger module and their assignment. | ||
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B16 (out) Time stamp clock C16 (out) D16 (out) 1 Hz | B16 (out) Time stamp clock C16 (out) D16 (out) 1 Hz | ||
- | ==== FPGA firmware ==== | + | ===== FPGA firmware |
The firmware of the trigger module is shown in the following files. The PDF file contains the schematic sheets, used for most of the design. The Verilog file contains the block dealing with CAMAC communications. | The firmware of the trigger module is shown in the following files. The PDF file contains the schematic sheets, used for most of the design. The Verilog file contains the block dealing with CAMAC communications. | ||
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- | ===== Time Stamping ===== | + | ====== Time Stamping |
The S800 trigger provides a vetoed 10 MHz clock signal (derived from the 40 MHz FPGA clock) used for time stamping. An external clock can also be used, after selecting the appropriate check box in the [[Trigger# | The S800 trigger provides a vetoed 10 MHz clock signal (derived from the 40 MHz FPGA clock) used for time stamping. An external clock can also be used, after selecting the appropriate check box in the [[Trigger# | ||
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- | ===== Configuration for S800 in tandem with other detectors ===== | + | ====== Configuration for S800 in tandem with other detectors |
In its standard configuration, | In its standard configuration, | ||
To incorporate an external detector in the S800 trigger logic, the same busy and end-of-event signals are required from its data acquisition system. This is to ensure that no live trigger signal is generated when any of the partners is busy or still processing an event. The 5 signals necessary between the S800 trigger and an external data acquisition system are the following: | To incorporate an external detector in the S800 trigger logic, the same busy and end-of-event signals are required from its data acquisition system. This is to ensure that no live trigger signal is generated when any of the partners is busy or still processing an event. The 5 signals necessary between the S800 trigger and an external data acquisition system are the following: | ||
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- | ===== Begin sequence ===== | + | ====== Begin sequence |
The internal " | The internal " | ||