Description Of The Communication Modes - Panasonic FP Series Programming Manual

Data transfer via communication ports

22.1 Description of the communication modes

Data transmission and reception can be carried out using the following communication modes. The
communication mode is set in the system registers of the PLC.
MEWTOCOL-COM
This communication mode uses the proprietary MEWTOCOL-COM protocol to exchange data between a
master and one or more slaves. This is called 1:1 or 1:N communication. A 1:N network is also known as a
C-NET. There is a MEWTOCOL-COM master function and a MEWTOCOL-COM slave function. The side that
issues commands is called master. The slave receives the commands, executes the process and sends back
responses. The slave answers automatically to the commands received from the master, so no program is
necessary on the slave. The MEWTOCOL-COM master function is not supported by all PLCs.
The master can be a PLC or any external device supporting the master function. To use the built-in master
functionality of the PLC, select MEWTOCOL-COM Master/Slave in the system registers and implement a PLC
program. The applicable instructions are F145_WRITE_DATA (see page 766) and F146_READ_DATA.
The slave can be a PLC or any external device which supports the MEWTOCOL-COM protocol. To use the
built-in slave functionality of the PLC, select MEWTOCOL-COM Master / Slave in the system registers. For 1:N
communication in a C-NET, the station number must be specified in the system registers of the slave.
Modbus RTU
This communication mode uses the Modbus RTU protocol to exchange data between a master and one or more
slaves. This is called 1:1 or 1:N communication. There is a Modbus RTU master function and a Modbus RTU
slave function. The side that issues commands is called master. The slave receives the commands, executes
the process and sends back responses. The slave answers automatically to the commands received from the
master, so no program is necessary on the slave.
The Modbus protocol supports both ASCII mode and RTU binary mode. However, the PLCs of the FP Series
only support the RTU binary mode.
Program controlled mode
With program controlled communication, the user generates a program which governs the data transfer
between a PLC and one or more external devices connected to the communication port. By this, any standard
or user protocol can be programmed.
Typically, such a user program consists of sending and receiving the data. The data to be sent and the data
received are stored in data register areas defined as send and receive buffers.
Sending can be controlled by the "transmission done" flag. For detailed information, see Flag Operation in
Program Controlled Communication (see page 757).
Sending includes generating the data for the send buffer and sending it using the
For all PLC types
instruction F159_MTRN (see page 741). For detailed information, see Sending Data to
External Devices (see page 733).
The "transmission done" flag can be evaluated using the IsTransmissionDone (see page
763) function. Or use the system variable sys_bIsComPort1TransmissionDone,
sys_bIsComPort2TransmissionDone, or sys_bIsToolPortTransmissionDone, depending on
the port.
Receiving includes processing the data in the receive buffer and preparing the system to receive further data.
Reception can be controlled by the "reception done" flag or by directly evaluating the receive buffer. For detailed
information, see Flag Operation in Program Controlled Communication (see page 757).
The "reception done" flag can be evaluated using the IsReceptionDone (see page 760)
For all PLC types
function. Or use the system variable sys_bIsComPort1ReceptionDone,
sys_bIsComPort2ReceptionDone, or sys_bIsToolPortReceptionDone, depending on the
port. The end of reception can also be determined by time-out using the
IsReceptionDoneByTimeOut (see page 761) function or by checking the contents of the
receive buffer.
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