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There are other eight DIP switches located at the PC board and can not be accessed from front panel. These
switches are usually only used during installation.
SW2-1:
Not used.
SW2-2:
Not used.
SW2-3:
Not used.
SW2-4:
Not used.
SW2-5:
Not used.
SW2-6:
Not used.
SW2-7: Not used.
SW2-8:
Off: The TC3420 is setup for an RS-422* application.
On: The TC3420 is setup for an RS-485*, 2/4 wire application.
The ground connector should connect to the user's device's signal ground.
For an RS-485 application, the transition time is set automatically by the TC3420 once a baud rate is selected
from the pull-down field on figure 16 on page 23. The baud rate is set according to the customer's application
needs and the TC3420 will adjust accordingly. For example, if you know the async data baud rate of your
application is for a 9600 baud, then the TC3420 will adjust automatically.
A termination resistor is usually necessary for RS-422 and RS-485 applications. Without proper termination,
the error rate of data transmission may be high due to an “echo” effect on the electrical connection. With
the addition of a termination resistor at the beginning or end of the electrical bus, this echo effect is greatly
reduced. The termination resistors are 100 to 130 ohm resistors located on the interface module inside the
TC3420. Two jumpers, identified as board locations “W1” & “W5” control the termination resistance on each
unit. “W5” controls the resistance for the unit’s receiver, while “W1” controls the transmitter’s resistance.
Proper line termination is usually accomplished by leaving the “W5” jumper intact at both ends of the link.
There is no termination resistor required for RS-232 applications.
*
Note:
Not used, for future release.
