Serial Protocols
ROS™ v3.5 66 RS400
2.2.5 Force Half Duplex Mode of Operation A “force half duplex” mode of operation allows use of extensions that create echo loops (as
optical loop topology that utilizes the RMC20 repeat mode function).
Figure 37: Optical loop topology
Figure 37 illustrates the optical loop topology that utilizes the RMC20 repeat mode function. The
repeat function will optically re-transmit any data received on the optical receiver, in addition to
any connected serial devices. As a result, any data transmitted from the master will be re-
transmitted optically to all the slaves.
This topology can be used for RS232, RS485, or RS422 multi-drop networks. In all cases, all
slaves have the repeat function (DIP position 4) ON, while the one connected to the RMC30 is
configured with the repeat function OFF. Used port on RMC30 must be in full duplex mode,
while parameter ForceHD (Force Half Duplex) parameter is turned ON.