INVENTIA MT-101, Руководство пользователя

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7.1. MT Slave mode
MT Slave is the basic and default operating mode of MT-101 module. In this mode, the
module makes all internal resources accessible and visible under Modbus ID defined in
configuration. PORT2 is not serviced.
Mode is employed where there is no need for communication with external devices via
PORT2. In other words, only module's own resources are used.
In this mode, data transmission to central system-master as well as communication among
modules operating in same mode is enabled.
7.2. Transparent mode
In this mode, the module receives data at serial PORT2, buffers it in memory and converts
to packets to send to defined recipients.
This mode allows data transmission without recognition of the protocol the data is sent in.
Data received at PORT2 is transmitted to all IP addresses defined in Authorized IP numbers
group when working in broadcast mode.
In order to reduce or eliminate transmitted data redundancy, two options are available:
•
packet routing - useful for unambiguous definition of where in transmitted frames the
recipient address is placed and how it is recorded without knowing the foreign
protocol. In that case, routing table can be created to eliminate redundant
transmissions.
•
transmission channel reservation - diminishes transmitted data volume provided that
multiple queries of one device are executed not knowing the foreign protocol. When
channel reservation is employed only the first query is sent to all modules defined in
Authorized IP numbers list. After reception of the response the module reserves, for a
defined time, the direct communication channel with the module that responded to
the last query thus creating a temporary point to point connection. The reservation
time is counted since reception of last GPRS packet. Consecutive packets received
from that module prolong channel reservation while sending packets does not prolong
the reservation. When channel reservation time is set to 0 [sec], the module does not
reserve channel and works in standard mode receiving and sending packets from all
defined remote units.
7.3. Modbus RTU Master mode
In this mode, the module cooperates with the device acting as MODBUS RTU MASTER.
The master sends queries addressed to Slave devices to module's PORT2 .
Upon reception of the frame at PORT2, the module verifies recipient device address. Since
module's own resources are available in Modbus RTU Master mode under Modbus ID
assigned to module, the instruction is carried out and replay sent to PORT2 (to the master)
when matched with address.
Frames with other Modbus ID addresses transmitted via GPRS are routed to other
recipients on the basis of a table assigning IP addresses to Modbus IDs (routing table -
redirection). In other words, MT-101 acts as a router of packets sent from Master to
remote Slave units. This mode enables creation of data acquisition system, where standard
queries generated by PLC controller or any other device working in Modbus RTU Master
mode. This solution is not recommended if master role is played by a PC running Windows
2000 or newer and collected data is used by applications capable of using data collected by
OPC or written in CSV or SQL format.
Following rules apply for Modbus RTU Master mode: