Signal Connection to External Devices
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DS1104 Hardware Installation and Configuration March 2004
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Connecting RS422/RS485 Devices
By default, the UART interface of the DS1104 is configured as an
RS422 transceiver. To use the UART as an RS485 transceiver you have
to connect the following pins (see below):
■ TXD signal to RXD signal
■ TXD signal to RXD signal
For proper operation of the UART interface you have to pay attention
to line termination and grounding.
Line termination The UART chip of the DS1104 does not provide line termination. If you
use the UART as an RS422 or RS485 transceiver, line termination is
essential, especially for faster data transfer rates and long cables. The
main reasons for correct termination are reflections at the ends of the
line, and the minimum transmitter load requirement.
DS1104
(RS485 mode)
T = Transmitter
R = Receiver
TXD
RXD
TXD
RXD
T
R
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