Subsystem Name:  GPS Time via TDC Module   part of WBS ???

Responsible Person:  Dan Edmunds  (MSU)

Agreed By:

Date:  27-March-2010

Document Version:  0.1 First Draft

Inputs:  [R]  GPS antenna signal

Outputs: [R]  1 pps, 100 pps, 10 MHz, and 40 MHz timing signals
         controlled by the GPS clock.  These signals will be
         provided at the appropriate signal level for external
         fanout to the Scaler and TDC DAQ systems.

         [R]  Provide signals to allow the high resolution bits
         of the GPS based event timestamp to be readout via a
         CAEN VX1190 TDC module.

         [R]  Provide standard Network Time Protocol (NTP) time
         service to allow the synchronization of computers in the
         HAWC DAQ system.

         [R]  With every trigger to the HAWC TDCs, this system will
         provide a GPS based timestamp that is readout in part via
         NTP controlled time in the DAQ computer and in part via
         the high resolution timestamp bits encoded in a normal
         TDC's event data.

Assumed Environment:  [R]  Rack space and power for the GPS clock.
                      TDC crate slot for the timestamp TDC module.
                      VME Crate space for the CAEN V1495 module that
                      makes the signals that control the timestamp
                      TDC.

Control/Configuration/Download:  [R]  There are numerous options of
                                 the GPS clock system itself and of
                                 the NTP server that need to be setup.

                                 [R]  The V1495 module will need to
                                 have its firmware downloaded and
                                 numerous control registers setup.

Functionality:  [R]  This system will provide a GPS controlled time
                base for the HAWC TDC and Scaler DAQ systems.  This
                consists of 1 pps, 100 pps, 10 MHz, and 40 MHz
                synchronous timing signals.

                [R]  With each trigger to the HAWC TDC system, this
                system will provide a GPS controlled timestamp that
                is readout from a standard TDC module in the same way
                as the rest of the TDC event data.

Performance Needed:  [R]  The time stamp will provide at the resolution
                     of CAEN TDC module (expected to be 200 psec) and
                     with an absolute accuracy of 1 usec rms.

Required/Goals for VAMOS:  none

Required/Goals for HAWC30:  none

Required/Goals for HAWC100:  [R]  This full system will be installed and
                             used in HAWC100.

Required/Goals for HAWC300:  [R]  This full system will be installed and
                             used in HAWC300.

Unit Testing Plans:  Initial integration and testing of the components
                     that make up this system will be done at MSU.

Integration Testing Plans:  The final "DAQ system readout testing" of
                            this system will be done at a location
                            that provides HAWC DAQ computer readout
                            of multiple TDC modules.

Baseline Design:  A CAEN 1495 FPGA module is used to form the control
                  signals that go to the TDC module that reads out the
                  event timestamp.  The GPS time code input to this
                  FPGA module is either parallel code or a direct
                  digital version of IRIG-B122 code.  Depending upon
                  the GPS clock that is selected the 40 MHz will
                  either be directly generated by it or else the 40
                  MHz will be generated in a module built at MSU.
                  Possible GPS clock modules include: Symmetricon IRIG
                  GPS clock and their model TCT parallel module,
                  Brandywine Communications model M210 with options
                  09, 15, and 27, or MicroSystem model SW1050 GPS
                  controlled NTP and IRIG server with either and
                  SR1322 or SR1321-1 IRIG-b to parallel

Equipment Budget:  ??

Personnel Budget:  ??