Re: hdlc error on SDI box..


Most commercially available NOAAPort receive systems use a 
serial_interface->satellite_demodulator typology to demodulate and stream 
data into a computer system.  The SBN itself is a one-way HDLC stream (HDLC 
is a protocol - or layer, if you will - of networking), so undoubtedly the 
SDI card is acting upon a serial input (more than likely the EIA530 output 
from an EFData SDR-54A satellite demodulator) and it does standard 
housekeeping that many commerically available serial cards do.

An HDLC error is indicative of a lot of things, but more than likely will be 
a CRC error caused by junk propogated on the serial port by a low signal to 
noise ratio - i.e. a noisy or lost signal - at the satellite demodulator.  If 
the SDI box gives you the capability, it would be best to check the signal 
stats from the satellite demodulator . . . and possibly repeak the reflector 
to optimize the signal.

It could also be a loose cable or connector, or an inability of the SDI card 
to keep up with incoming packets and thus receiving incomplete packets 
because of timing.

Good luck.


On Tuesday 09 July 2002 13:07, Robert Mullenax wrote:
> Quick question for those with an SSEC NOAAPORT SDI box..Do you know what
> hdlc error
> means?  We missed data last night and the terminal on the SDI box is
> scrolling "NMC:.....hdlc error".
> Thanks,
> Robert Mullenax
> Robert Mullenax
> Weather Systems Administrator
> Universal Weather and Aviation

Stonie R. Cooper
Planetary Data, Incorporated
ph. (402) 782-6611