Rs485 Interface (Option); Transmission Protocols; Bus Structure; Shielding - janitza Prophi Operating Instructions Manual

Reactive Power Controller

RS485 Interface (Option)

Transmission protocols

Two transmission protocols are available for the connec-
tion to an existing field bus system:
0 - Modbus RTU (Slave) and
1 - Profibus DP V0 (Slave) .
With Modbus protocol you can have access to the data of
table 1, and with Profibus protocol you can have access
to the data of table 2.

Bus structure

All devices are connected in bus structure (line). In one
segment up to 32 participiants can be assembled. At the
end and the beginning of each segment, the cable must
be terminated by resistors. In Prophi you can activate
these resistors with two plug-ins.
For more than 32 participiants you must use a repeater
(line amplifier) to connect the single segments.

Shielding

For connections via RS485 interface, you need a pro-
tected and twisted cable. To achieve a sufficient protec-
tion result, the shielding must be connected at both ends
extensively to the housing or parts of the cabinet.
Cable specifications
The maximum cable length depends on cable type and
transmission speed. We recommend cable type A.
Cable parameter Type A
Impedance 135-165Ohm
(f = 3-20MHz)
Capacity < 30pF/m
Resistance < 110 Ohm/km
Diameter >= 0,34mm2
(AWG22)

Cable length

The following table shows the maximum cable length in
meters (m) for various transmission speed
.
Baud rate (kbit/s)
Cable type 9.6 19.2
Type A 1200 1200 1200 1000 400
Type B 1200 1200 1200 600
Page 14
Typ B
100-130Ohm
(f > 100kHz)
< 60pF/m
-
>= 0,22mm2
(AWG24)
93.75 187.5 500 1500
200
200 70

Terminal resistors

If Prophi is connected to the end of the bus cable, the
bus cable must be terminated at this point with resistors.
The required resistors are integrated within the Prophi
and are activated in position ON.
Termination
392R 221R
GND
ON
GND
Prophi
10200740
Diagr. Connection RS485 interface
= Key 1 = Key 2
392R
+5V
OFF
B
23
A
22
21
= Key 3