Pixsys TD240 series, Руководство по эксплуатации

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9 Communication protocols
The TD240 can communicate with all devices that support the
following serial protocols:
•
ModBus RTU
•
Nais Matsushita master
The terminal has 2 serial ports of communication (EXP, COM2),
analyzed from the electrical point of view in chapter 3. The ports
are each managed in a different manner and will be analyzed
separately.
9.1 Managing the communication port
The communication between the TD240 and other devices is
managed by the PLC part of the terminal, thus the configuration of
the port and the instructions must be implemented in the
development environment PLProg 4.xx. Generally the coils of the
Ladder diagram are executed following the sequential order
written in the diagram itself. The instruction related to the coil at
line “n+1” is not executed until the full completion of the instruction
related to the coil at line “n” (for coils positioned in the same
column).
The control of transmission and reception of data is instead
asynchronous with respect to the cycle of execution of the
Ladder code.
When an instruction of read/write of a device must be executed
(line “n”), control passes immediately to the next instruction (line
“n+1”), without waiting for the data to be effectively read/written.
The effective transfer of the data in the serial line is executed in a
manner that is independent to the normal scan of Ladder code, in
different times according to the port that is used.