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Introduction: Pulse Code Modulation (PCM) Commutator is specifically designed for transmitting PCM telemetry data. National Instruments reconfigurable I/O hardware and LabVIEW FPGA software are used to develop the PCM Commutator. This provides for various parameters of the communication stream to be customized based on specific application needs. The FPGA module used operates on a 40MHz clock and provides high accuracy bit encoding over the entire frequency range of the PCM Commutator. |
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The data to be transmitted is stored in a Current Value Table (CVT) on the FPGA memory. The CVT contents can be changed on the fly by the user using either the GUI provided or programmatically. The ability to change the CVT table programmatically indicates that other applications (example: data acquisition applications) can directly pass data to the software for PCM telemetry. The Commutator memory is large enough for most commutation applications and the Index Matrix Table (IMT) can have a maximum of 16 KB of data. The FPGA module used has multiple digital lines so the same stream can be generated on multiple channels. |
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The GUI provided with the PCM Commutator is user friendly and easy to use. The user can save configured PCM formats to disk for later use. The software has provision for real time display of the transmitted stream. The user can also enable or disable the stream on the fly.
The PCM Commutator is available in PCI, cPCI, PXI and stand-alone form factors. |
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- Output format - NRZ-L (can be customized for other formats)
- Output Levels - Single Ended TTL
- Output Data Rates - Upto 2 Mbps
- Word length - Upto 16 bits per word (can be customized for 32 bits per word)
- Minor Frame Length - Upto 15,872 words per minor frame
- Major Frame Length - Upto 1024 minor frames
- Frame Sync Pattern - Upto 32 bits (any series of 0's and 1's can be used)
- Major Frame Sync - SFID
- Graphical User Interface developed using LabVIEW for ease of use
- Real time display of transmitted data
- Facility to save configured PCM formats for later use
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