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the MQTT broker. Sample content for the most extensive option (when 91: MqMo = FuLL , maximum size 99B):
"AR6x2_1;PV=36.6 °C;MV1=100 %;MV2=100 %;MV3=0 %;cstat=0x0000;outA=7.320 mA;BIN=0" (AR6x2_Addr =
device name; PV = measurement value and unit; MV1 = value of the control signal for output 1; MV2 for the output
2;MV3 for output 3; cstat = work status of control algorithms, description in chapter 11.5;outA= analog output
signal value mA / V; BIN = binary input status, 0 = closed, i.e. active).
Additionally, in order to optionally authorize the connection, the following fields are set in the MQTT packet: client
ID (created accordingto the template "aparMAC ", where MAC is the EUI-48 hardware address of the controller,
e.g."aparFCC23D21C54A") and user name (as "aparPASS ", the last 2 digits of parameter 70: PASS, eg " apar11") and
password (parameter 70: PASS ).
Protocol parameters useful for advanced needs: version 3.1.1, QOS = 0, retain = 1, keep alive = 0 (off).
In the event of frequent disconnection with the broker , check the reliability of the network/internet connection
(switch), test the possible impact of the message publication period (extend, recommended> 5s, parameter 97:
MqtP), as well as MODBUS-TCP communication (temporarily stop if in use).
11.2. MODBUS–TCP SERIAL TRANSMISSION PROTOCOL
The MODBUS-TCP protocol is available for the Ethernet (RJ45) interface and uses the TCP/IP transport layer.
Parameters used by this service, such as the TCP port number, are described in chapter 8, Table 8, point VIII.
The timeout for the MODBUS-TCP transmission, after which the open but unused port is closed, is 60s.
Available functions: READ - 3 or 4, WRITE - 6
Table 11.2.1. MODBUS-TCP protocol request frame format for the READ and WRITE functions (frame length -
12B)
MODBUS protocol header (7 bytes) Function
code
(READ or
WRITE)
register address
from Table 11.5
(chapter 11.5)
number of registers to
read (1 ÷ 13) or value of a
register to write
Transaction and protocol
identifiers
Length field
(value = 6)
Unit ID
4 bytes 2 bytes 1 byte 1 byte 2 bytes (HB-LB) 2 bytes (HB-LB)
Example 11.2.1. Reading a register with address 0: 0x00 - 0x00 - 0x00 - 0x00 - 0x00 - 0x06 - 0xFF - 0x04 - 0x0000 -
0x0001
Table 11.2.2. Response frame format for the READ function (minimum frame length - 11 bytes):
MODBUS protocol header (7 bytes)
Function
code
(READ)
number of bytes
in the data field (2
÷ 26)
data field - register
value (2B)
Transaction and protocol
identifiers
Length field
(max 29)
Unit ID
4 bytes 2 bytes 1 byte 1 byte 1 byte 2÷26 bytes (HB-LB)
Example 11.2.2. The response frame for the register value equal to 0:
0x00 - 0x00 - 0x00 - 0x00 - 0x00 - 0x05 - 0xFF - 0x04 - 0x01 - 0x0000
Table 11.2.3. Response frame format for the WRITE function (frame length - 12 bytes)
copy of the query frame for the WRITE function (Table 11.2.1)
The error codes are the same as for the MODBUS-RTU protocol (Table 11.4.5)
Example 11.2.3. Error frame for a non-existing register address to be read:
0x00 - 0x00 - 0x00 - 0x00 - 0x00 - 0x05 - 0xFF - 0x84 - 0x02 - 0x0001
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