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TC2200R/S Bus
User's Manual
Chapter 1 - Overview
Rev. 2.2
Description
The TC2200R/S and TC2201R/S are multi-drop fiber optic modems that convert electrical signals to fiber
optic signals (and vice-versa). At least one TC2200 (Master) unit and one TC2201 (Slave) unit are required
to communicate with each other. The Master unit is connected to a Host computer (or controller), while the
Slave unit can be connected to an RTU (Remote Terminal Unit), PLC (Programmable Logic Controller) or
any poll-response type device. Typical applications include SCADA, process control, traffic control and
energy management.
In a poll-response environment, the host controller broadcasts polling messages to every RTU. Because the
polling message is embedded with a specific RTU's ID (or address), only the RTU with the correct ID
responds to the Master's polling. The Master (TC2200) unit's function is to convert the electrical signals
(RS-232, RS-422 or RS-485) from the Host controller to fiber optic signals, then transmit the signals in both
bus directions to the Slaves, as illustrated in Figure 1.
The first Slave in the bus intercepts the Master's broadcast message and forwards it to its downstream Slave
unit. Each subsequent Slave forwards the broadcast message until it reaches the last Slave in the bus
(designated as the End Unit).
Figure 1. Master Unit's Broadcast & Receive Directions
The Slave (TC2201) unit's function is similar to the Master's; it converts fiber optic signals from the Master
back into electrical signals (RS-232, RS-422 or RS-485) so that the RTU or PLC connected to the Slave
receives the polling message from the Host. The Slave unit then converts the electrical response signals
from the RTU or PLC to fiber optic signals, then transmits them back to the Host (via the Master) in both
bus directions, as illustrated in Figure 2.
Figure 2. Slave Unit's Response & Receive Directions
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