Lenze smd Series Drives - Manual (Page 8)

RG-SDMOD 4
Introduction
2.2.3 Network Termination
For an RS-485 network it is essential to install the specified termination resistors (120 W), i.e. one at both
ends of a network segment. Failure to do so will result in signals being reflected back along the cable which
will cause data corruption. An external 120
W 1/4W resistor can be connected as shown in Figure 3.
U V W
L1 L2
8 9 20 28 E1 E2 E3 K14 K12
+10
V
+12
V
CO
M
AIN
7 71 72
L3
20 A1 62
TXA TXB
COM
Connect to
drive earth
(PE)
120 Ω
1/4W
Figure 3: Network Termination Resistor
2.3 Modbus Details
A. smd Drives running the Modbus communication protocol use the RTU (Remote Terminal Unit)
transmission mode and are slaves only. Therefore, the device communicating with the drives must
be a Modbus Master. The baud rate is 9600. The default setting is no parity (two stop bits). There are
provisions for: No parity, 1 stop bit (PV507); Odd parity, 1 stop bit; and Even parity 1 stop bit as well.
The bit sequence is:
DATA
Start bit 1 2 3 4 5 6 7 8 Stop bit Stop bit
B. At this time the smd drive does not support the broadcast function of the protocol.
C. IMPORTANT NOTE: Modbus 3X and 4X Registers are numbered starting at 1. However, when transmitted
to a slave over the serial link, the actual address transmitted is one less. This is because the addresses
are numbered starting from 0. The
smd register numbers are also numbered starting from 0. Therefore,
smd register numbers always correspond exactly with the address transmitted. As a result, MODBUS
REGISTER NUMBERS ARE ALWAYS ONE GREATER THAN
smd REGISTER NUMBERS. WHENEVER THE
WORDS “REGISTER #xx” APPEAR, IT SHOULD BE ASSUMED THAT THEY MEAN “ smd REGISTER xx” and
the Modbus Register number will be one larger. In some instances we may show both for clarity. For
example: “Register #24 (Modbus Register #25) . . .”