Interfacing a HALComm ST-8000 HF modem via the Black Cat Systems
MIL-STD-188C synchronous serial interface
Black Cat Systems MIL-STD-188C synchronous serial interface
The ST-8000 has a built in UART-based FSK regeneration circuit that
can convert ASCII and BAUDOT asynchronous serial data to serial data
at a different speed and output it over an RS-232 port. However, the
regeneration circuit cannot output synchronous serial codes.
A Black Cat Systems MIL-STD-188C synchronous serial interface can be
used to convert demodulated synchronous FSK and clock data from the
ST-8000 and convert it to asynchronous RS-232 data at a higher
baudrate via the USB interface.
The necessary cable has the following connections:
ST-8000 Black Cat Systems
pin name name
--- ----- ----
3 RS-232 rxd rxd
17 rx clock clock
7 ground ground
Note that the RS-232 rxd pin is used rather than the MIL-188C rxd pin.
This is because the signals present on the MIL-188C pin have a -3V DC
offset that prevents it from working successfully with the USB adaptor.
With the default clock jumper setting inside the ST-8000, the clock
on the USB adaptor should be set to the falling edge setting.
When the ST-8000 is used to demodulate synchronous data note that the
'regen' switch must be in the 'off' position.
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Last modified May 31, 2005