7700 MultiFrame Manual
7707DT RS-232/422/485 Fiber Data Transceiver
Revision
1.8
Page - 29
7.2.2. MPK Interface to RS-485
A second interface method exists, which allows Control Panels to be located on both ends of the 7707DT
fiber link. This method is only advantageous should available ports be limited on the System Controller.
Otherwise, Control Panels connected on the System Controller side of the 7707DT fiber link can be moved
to a spare port, and the previously described method used.
The 7707DT can be configured to operate with RS-485 interfaces. This type of interface allows the output
signal to be placed in a high-impedance state, as required for direct connection to Control Panel outputs.
Therefore, when this method of interface is used, Control Panels may be connected on both ends of the
7707DT fiber link. The RS-485 interface protocol accommodates only one balanced pair of wires.
Therefore, two channels of the 7707DT must be used; one for each direction of data transport.
Only the channel used to transport data in the Control Panel to System Controller Direction should be
configured for RS-485. This channel should be configured for a data rate of 1200baud. The channel used
to transport data in the System Controller to Control Panel direction should be configured for RS-422.
Refer to the manual for details about configuring each channel.
Figure 7-7 shows a block diagram describing this method of interface. Figure 7-8 describes pin-for-pin
connections.
7707DT
Control Panel
Control Panel
Control Panel
Jupiter System Controller
7707DT
Set to
RS-422
Set to
RS-422
Set to
RS-485
Set to
RS-485
Figure 7-7: MPK Interface to RS-485