37
CONTROL SYSTEM
The unit can communicate on a serial line using the
Modbus
communication protocol with
RTU
coding.
The unit can be connected to an RS485 network by means of the serial interface supplied as an accessory, and reply to the requests
of any master device connected to the network.
Serial line settings
The serial line must be set as follows :
•
baud rate
:
9600
•
data bits
:
8
•
stop bits
:
1
•
parity
:
even
All the devices connected to the same serial line MUST use the same settings.
Device address
To communicate properly, each device connected to the serial network must have an univocal address (
“Modbus individual address”
)
contained between 1 and 247. This address can be set by modifying the parameter
CF63
.
Modbus commands
The Modbus commands implemented by the controller are :
•
parameter reading
3
(Hex 03 : Read Holding Registers)
•
parameter writing
16
(Hex 10 : Write Multiple Registers)
Addresses table
All the available resources are stored in the controller as WORD (2 byte) and therefore require the reading or writing of an entire
Modbus register. According to the Modbus protocol, to identify a register of address X the address X-1 must appear in the message.
Some registers contain more than one piece of information : in this case the bits representing the resource value are identified by
means of the number of bits used (“Bit number”) and by the least significant bit (“Lsb”). In the writing operation for these registers it
is necessary to read the current register value, modify the bits representing the resource concerned and rewrite the entire register.
Example
.
Bit number
=
4
Lsb
= 7
Resource value =
3
The resources can be only read (R), only written (W) or read and written (RW).
To interpret the value written in the register it is necessary to consider the value of CPL, EXP and UM :
CPL : if the register represents a number with sign (CPL = Y) carry out the following conversion :
0
=
register value
<
32767 :
resource value = register value
32768 =
register value
<
65535 :
resource value = register value – 65536
EXP : indicates the exponent of the power of 10 to be multiplied by the register value to obtain the resource value.
MU :
indicates the unit of measure of the resource
IMPORTANT .
DO NOT modify any parameter not indicated in the table provided or indicated as a read only parameter (R), otherwise
the warranty will be invalidated.
15 14 13 12
11
10
9
8
7
6
5
4
3
2
1
0
0
1
1
0
1
0
0
1
1
1
0
1
1
0
1
0
EXP
Moltiplicatore
-2
10
-2
0,01
-1
10
-1
0,1
0
100
1
1
10
1
10
2
10
2
100
Serial communication