Macurco DVP-1200, Manual

Page: 16 / 68

Macurco TM DVP-1200 Manual
REV – 1.3.1 [34-8708-4770-7 ] 15 | P a g e
Table 3-3 – Dip Switch Settings
3.2.4.4 Topology
An RS485-MODBUS configuration without repeater has one trunk cable, along which devices are connected, directly (daisy
chaining) or by short derivation cables. The trunk cable, also named “Bus”, can be long. Its two ends must be connected on
“Line” Terminations. (see Section 3.2.4.5 Line Termination – End of Line Resistor ). The use of repeaters between several RS485-
MODBUS is also possible.
The DVP-1200 has three Modbus termination blocks that will accept two trunk cable connections allowing for two MODBUS
communication lines. The Trunk cable must be wired in parallel from the panel to the end of line with no off shoots “T-tapping”.
3.2.4.5 Line Termination – End of Line Resistor
The MRS-485 and DVP-1200 are wired in the standard 2W-Modbus circuit definition with selectable built-in terminating
resistors at the ends of the RS-485 bus. The MRS-485 and DVP-1200 provide integral termination for the end of line resistors
(EOL). The terminations use 4-pin connector with a jumper to select termination: The user selects no termination or one of the
two Modbus line termination options. The MRS-485 and DVP-1200 have two-line termination options (100 Ohm and 120 Ohm)
available.
Place the EOL jumper on one of the following positions:
N = No termination (default)
2 = 120 ohm
1 = 100 ohm
Figure 3-8 – EOL Jumper Settings
3.2.4.6 Baud Rate
At the baud rate of 19200 (default baud rate for Macurco MRS-485 and DVP-485) and with cables less than 1,000 ft. in length,
termination resistors are not recommended.
At the baud rate of 19200 and with cables longer than 1,000 ft., termination resistors are recommended.
It is recommended to use an RS-485 type of cable and 120 ohms for termination resistor.
An RS-485 network requires a 3-wire cable: a twisted pair and a third wire. It is difficult to tell whether shielding is required or
not in a particular system until problems arise, so it is recommended to always use shielded cable.
When using termination resistors use only 2 resistors, one at each end of the RS-485 transmission line (i.e. 1 at the DVP-485B
and 1 at the last/farthest MRS-485).