Comtech EF Data SFC4200 - Manual (Page 55)

SFC4200/SFC1275G Synthesized Frequency Downconverter Electrical Interfaces
TM054 - Rev. 4.0 5-5
Figure 5-2 shows the AS/3048 Controller. Figure 5-3 shows the locations on the controller of the
various jumpers required to configure the hardware for RS-232, RS-422, Full-Duplex RS-485 and
Half-Duplex RS-485 (Figures 5-3 through 5-6). To make these changes, remove the top cover
and locate the AS/3048 Controller. Some software configuration changes must also be made by
the operator to implement the RS-422/-485 or multipoint RS-232 modes of serial operation. The
theory of operation for multipoint requires that the M&C Computer Transmit Port be connected in
parallel to all of the Receive Data Ports of the various converters. Likewise, the transmit ports of
the various converters must all be connected in parallel and tied to the Receive Data Port of the
M&C Computer. To prevent any one Converter Transmit Port from acting as a low impedance,
thus hanging the bus, each transmit port of each converter remains in a high impedance state
until asked by the M&C computer to transmit.
Figure 5-2. AS/3048 Controller