Instructions

UM-0085-B09 DT80 Range User Manual Page 198
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RS485 Connection
RS485 uses half duplex differential signalling: there is just one pair of wires, which is used for both transmit and receive.
Be sure to observe the correct signal polarity, as shown in the diagram. Some devices label their terminals as A or B,
some as + or –.
Notice that with RS485, all devices including the DT80 are wired symmetrically: there is no distinction between "master"
and "slave", at least from a wiring perspective.
An RS485 network should normally be cabled as a single linear "backbone", with relatively short "stub" connections to
each device. For long cable runs or high baud rates a 100Ω termination resistor at each end of the main cable is
recommended.
Figure 80: Serial sensor port RS485 connection
Configuring the Serial Sensor Port
The following parameters need to be set for the serial sensor port:
• port mode (RS232, RS422 or RS485) – default is RS232.
• baud rate (data transfer rate in bits per second) – default is 1200.
• serial framing format (number of data bits, parity type, number of stop bits) – default is "N,8,1", i.e. no parity, 8
data bits, 1 stop bit.
• flow control (mechanism for one computer to tell the other to stop sending) – default is no flow control
• port function (protocol to be used: command, PPP, Modbus or generic serial) – default is generic serial
PROFILE Settings
To view the current serial sensor port settings use the following command:
PROFILE SERSEN_PORT
[SERSEN_PORT]
*BPS = 9600
DATA_BITS = 8
STOP_BITS = 1
PARITY = NONE
FLOW = NONE
MODE = RS232
FUNCTION = SERIAL
which lists the current baud rate, framing format, flow control, port mode and port function. An asterisk indicates a non-
default setting. See Profile Settings (P264)) for more details.
If required, these settings can be changed using individual
PROFILE commands, i.e.:
PROFILE SERSEN_PORT key=value
The following keys are defined:
Key
Value
Default
BPS
baud rate. Use
300, 600, 1200, 2400, 4800, 9600, 19200, 38400
or
57600.
1200
DATA_BITS
can be
7
or
8
8
STOP_BITS
can be 1 or 2
1
PARITY
can be N (none), O (odd) or E (even)
N
FLOW
NONE
(no flow control)
SOFTWARE (XON/XOFF)
HARDWARE
(RTS/CTS)
NONE
MODE
signal standard:
RS232, RS422
or
RS485
RS232
FUNCTION
port function (see below)
SERIAL