Siemens LMV5 Series Technical Instructions

LMV Series Technical Instructions
Document No. LV5-10
00
SCC Inc. Page 1 Section 8
8-1: Modbus
Master-slave principle
Communication between
Modbus users takes place according to the master-slave principle. The AZL5
always works as a slave.
Data Transmission
Transmission mode (RTU)
– The transmission mode used is RTU (Remote Terminal Unit)
– Data is transmitted in a binary format (he
xadecimal) with 8 bits
– The LSB (least significant bit) is transmitted first
– ASCII operating mode is not supported
Structure of data blocks
All data blocks use the same structure with the following four fields:
Slave Address Function Code Data Field Checksum CRC16
1 byte 1 byte x byte 2 bytes
Slave A
ddress
Device address of a certain slave
Function
C
ode
Function
selection (reading / writing words)
Data F
ield
Contains the following information:
- Word address
- Number of words
- Word value
Checksum
Identification of transmission errors
Checksum (CRC16)
The checksum (CRC16) is used to detect transmission errors. If, during evaluation, an error is detected,
the relevant device will not respond.
Calculation
scheme
CRC = 0xFFFF
CRC = CRC XOR ByteOfMessage
For (1 through 8)
CRC = SHR (CRC)
if (flag shifted at right = 1)
then
CRC = CRC XOR
0xA001
else
while (not all ByteOfMessage handled)

The low-byte of the checksum is transmitted first.
HOME

Siemens LMV5 Series Specifications

General

Brand	Siemens
Model	LMV5 Series
Category	Control Systems
Language	English