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Communications Using Memory Links Section 1-5
The NT link is compatible with the host link. The NT631/NT631C screen data
and PLC programs used with the host link direct connection method can be
used with the NT link method as they are.
1-4-4 Connecting to Other Companies’ PLCs
Installing a system program for multi-venders by using a specific system
installer enables the NT631/NT631C to be connected to the PLCs of other
models in direct connection. This system installer is supplied with the Support
Tool (NT-ZJCAT1-EV4).
Compatible PLC The NT631/NT631C can be connected to the following model PLCs.
• Mitsubishi A-series programmable controller (computer link module)
• Mitsubishi FX-series programmable controller
• SLC 500 Series by Allen-Bradley
• 90-20 and 90-30 Series by GE Fanuc
• S7-300 and S7-400 Series by Siemens
For details on the procedure for connecting to other model PLCs, refer to the
PLC Connection Manual or NT31/631 Multi Vendor Connection Manual.
1-5 Communications Using Memory Links
In this section, a communications method other than the direct connection,
called the memory link, is discussed.
1-5-1 Memory Link
Memory link is a method to send and receive data between a personal com-
puter or a FA computer and the NT631/NT631C by using RS-232C/422A
communications.
In memory link, there is an area called PT Memory, as shown below, inside
the NT631/NT631C, and this area is treated as a virtual area on the PLC. This
allows PT memory and the display elements of the NT631/NT631C to make a
quasi-direct connection. By sending a command for the memory link, the host
can make the NT631/NT631C execute processes through PT memory. Fre-
quently used commands are kept handy for read and write tasks of the
numeral memory table, character-string memory table, and bit memory table.
In the memory link method, the only difference is that the NT631/NT631C
finds its communications target inside instead of outside. In the memory link
method, therefore, change of the target is all that is needed to be capable of
using the exact screen data that is acquired by the direct connection. (With
the NT631/NT631C, the Support Tool must be used to convert the data to
screen data for the memory link.)
When compared to the direct connection of the host link or NT link methods,
the memory link method has some restrictions regarding the use of some
functions, as described below.
Lamp
PT memory
PT
Direct connection
RS-232C/422A
communications
Numeral
memory
table