Multi-Master Units (Optinal) - TC Communications TC2200R User Manual

Multi-Master Units
If the units were ordered for a Multi-Master
Multi-Drop application (optional), the following
information applies to their configuration. The
Multi-Master units are (by default) DCE de-
vices. The internal SW1 DIP switch functions
and some features for Multi-Master units differ
slightly from Single-Master models.
SW1_1 & SW1_2 disable the "RxA" & "RxB" optic receivers when switched to the Left position. These
two switches should be set according to the position of the unit in the bus. Typically, "RxA" is disabled on
the first unit (Master or Slave) and "RxB" is disabled on the last unit (End unit). All other units (between
the first and last units in the bus) should have SW1_1 & SW1_2 in the Right position for normal multi-drop
operation.
The Master unit (TC2200) and Slave unit (TC2201) are interchangeable by sliding SW1_3 to the Left (Slave)
or Right (Master) position. The front panel's "MASTER" or "SLAVE" LED will light to indicate which
configuration the unit is utilizing. The Auto-Master Mode allows each unit to temporarily act as a Master unit
until the attached device stops transmitting for a predetermined amount of time (based on the baud switch
settings of SW1_7 & SW1_8).
The TC2200/2201 has a built-in Anti-Streaming function. Anti-Streaming can prevent a defective RTU from
blocking out an entire response channel; once activated, the electrical signal from the defective RTU is
blocked and the entire response channel is disconnected from the Slave unit. This feature can be disabled
by sliding SW1_5 to the Right position.
SW1_6 on the internal DIP switch is not used and should be kept in the Right (Off) position.
SW1_7 & SW1_8 control the RS-485 transition timer setup and the Master/Slave transition time. For a 2-
wire or 4-wire RS-485 interface, the electrical signal bus will automatically transition to high impedance after
transmitting. These two switches establish the duration period (after the last bit is transmitted) before the
RS-485 driver transitions to the high-impedance receiver mode.
The transition timer also establishes the interval of time that Master unit "holds" the bus (after the last data
bit is received from the local RTU) before automatically transitioning back into the Slave mode. The
transition timer should be set according to the following table (Default = both Off):
38.4K & up
Baud SW1_8
On
9600
Off
19.2K
On
Figure 9. Transition Timer Setup Table
SW1_6
SW1_7
Off
Not Used
On
Not Used
On
Not Used
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TC2200R/S Bus
User's Manual
Rev. 2.2