GPS Timing Board with VME Interface
- GPS-synchronized timecode generator
- GPS, IRIG-A, IRIG-B, NASA36, XR3, and 2137 timecode reader
- IRIG-B output
- Time-Tag input
- Two configurable pulse rate outputs
- 1 MHz TTL output
- Freewheel capability
- Continuous parallel time output
Product Overview
The TSAT-VME is a complete system package, including the GPS Receiver/Antenna (housed in a common enclosure), a 100-foot antenna cable, and a VME circuit card assembly.
The board synchronizes its on-board clock to the incoming timecode. The on-board clock’s time is also provided as an IRIG-B output. Other features include a time-tag TTL input, a 1Mhz TTL output, and two user-configurable TTL pulse rate outputs.
The unit automatically tracks GPS satellites. In addition to time, the host computer can also read longitude, latitude, and elevation. In the unlikely event that satellite reception is lost, the board will continue to increment time (“freewheel”) until reception is re-established. A propagation delay offset may be specified to compensate for the antenna cable delay.
A front panel indicator lights when the unit is tracking satellites. An optional seven-segment LED display shows day and time in DDD:HH:MM:SS format (order Option –D). The GPS satellites provide worldwide coverage in all weather. The received time is accurate to within 1mS of UTC. This is useful for synchronizing processed or data collection at distant sites.
VME Interface
The board supports A32, A24, and A16 addressing modes using the standard address modifiers. Other address modifiers can be supported by custom modifications.
All board functions can be generated when time is available or when a time-tag event has occurred. The interrupt level (IRQ1–IRQ7) is selected by jumpers, or the user can disable interrupts and poll the status register instead. Customized periodic interrupts are also available.
The VME bus specification permits Rows A and C of the P2 backplane connector to be user-defined. The on-board clock time is output as 54 TTL signals on these pins; this provides continuous time with zero latency. To prevent any possible conflict with other user-specific boards in the system, order the board with Option –32P2 to eliminate these outputs.
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