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Interfacing a HALComm ST-8000 HF modem via the Black Cat Systems MIL-STD-188C synchronous serial interface

USB Sync 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
TERMINAL              MIL-188C
DATA                  adaptor
---------             -------
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