Setup, Network and Communication Manual ESTM / ESTM-L
17-88C1-*
11-88C1-7D0002
Notice
Technical data subject to change without notice.
No claims for damage arising from alternations, errors or misprints shall be allowed.
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5. Modbus RTU / RS485 Interface
5.1 Line
For daisy chaining the ESTM/ESTM-L provides one in and one out Modbus terminal. For end termination, a resistor is already
included. To terminate the bus at the last device, a jumper needs to be installed
at the “
Modbus Out
” terminal between Terminal
“B”
and
“T”.
5.2 RS 485 Interface
The controllers are provided with a RS485 serial
communication interface.
Description
Data
Data bit:
8 bit
Parity:
NO parity
Stop bit:
ONE stop bit
Baud rate:
9600
5.3 Modbus Specifications
5.3.1
Modbus Function Code
Modbus uses Different function codes to transfer data
between master and Slave device. The ESTM/ESTM-L uses
the following function codes for data transfer:
Modbus Function code
Description
FC 1
read coil
FC 3
read holding register
FC 4
read input register
FC 5
write single coil
FC 6
write holding register
5.3.2
Bit Numbering
MSB
to
LSB
1
0
0
0
0
0
0
1
5.3.3
Data Types
Data types
Description
bool
true/false [1=true; 0=false]
int 16
signed
integer
16
bit
[
−32768 to 32767]
uint 16
unsigned
integer
16
bit
[0 to 65535]
uint 32
unsigned
integer
32
bit
[0 to 4.294.967.295]