3701RE: [V4Protocol] H4 Protocol spec for FEC and ARQ posted to V4Protocol files section.
- Nov 27, 2013
Thanks to Ron’s feedback I found the bug that was not blanking out the CRC check byte from displaying in the ARQ ID frame…A simple fix which I have operating now. The concept is fairly simple …only adds one byte (128 ms) to these frame: A End of Transmission (Hex 04) is inserted just before the CRC check sum… The Check sum byte (which can be any 8 bit value based on the data) is then “hidden” since the station in FEC mode sees a EndOfTransmission character directly in front of the CRC byte. That EOT forces a monitor in FEC mode to stop processing characters so the CRC character is not shown. This should all work OK now. Stations using ARQ have a more complex capture, decode and display mechanism so can decode and compute the CRC check and basically ignore the EOT in the ARQ ID frame.
The only frame that this won’t work for is the ARQ BINARY frame since by definition the Binary frame can include any of the 8 bit values and these may “print” in strange ways on a station monitoring in FEC mode. But pure BINARY data will always print funny since it contains all available 8 bit values.
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