NAiS FP Series, User Manual

Page: 148 / 326

FP
Σ
8.1 Computer Link
8 - 3
8.1 Computer Link
This section explains about overview of computer link function.
8.1.1 Overview of Function
Computer
Command message
Response message
FP
Σ
With a computer link, first an instruction (command) is sent
from the computer to the PLC, and then the PLC sends a
reply (response) back to the computer.
Figure 140: FP
Σ
Overview of computer link function
What is the computer link?
A computer link is a function that carries out communication between a computer and
PLC, making it possible to monitor and control the PLC operating status from a
computer.
Conversation is carried out between the two by instructions (commands) being sent
from the computer to the PLC, and the PLC replying (sending response messages)
back to the computer.
A MEWNET exclusive protocol called “MEWTOCOL-COM” is used to exchange data
between the computer and PLC.
The communication speed and transmission format are specified using system
registers No. 413 (COM. 1 port) and No. 414 (COM. 2 port).
Program for computer link
To use a computer link, a program should be created that enables command messages
to be sent and response messages to be received on the computer side. No
communication program is required on the PLC side.
Programs for the computer side should be written in BASIC or C language, based on
the MEWTOCOL-COM format. MEWTOCOL-COM contains the commands used to
monitor and control PLC operation.