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Communications with the Host Section 1-4
Besides the 1:1 NT Link method, in which one PLC is connected to one PT,
the NT31/NT31C can also use the 1:N connection NT Link method, which
allows a maximum of eight PTs to be connected to one PLC port.
PLCs that can be connected with the 1:N connection NT Link method are as
follows: CQM1H, C200HX/HG/HE (-Z)E, CS1G/CS1H-E(V1), CS1G/CS1H-H
CS1D, CJ1G/CJ1H/CJ1M PLCs.
The NT31/NT31C also supports OMRON’s high-speed 1:N NT Link that pro-
vides faster 1:N communications. The only PLCs that support the high-speed
1:N NT Link are the -EV1 and higher versions or the high-speed versions of
the CS1G/CS1H PLCs and the CS1D and CJ1G/CJ1H/CJ1M PLCs.
In the following sections, the term NT Link is used to refer to the NT Link com-
munications method in general, the term 1:1 NT Link is used to refer specifi-
cally to NT Links with a 1:1 connection, and the term 1:N NT Link is used to
refer to both standard and high speed NT Links with 1:N connections. When
necessary, the standard 1:N NT Link is distinguished from the high-speed 1:N
NT Link.
Features of the NT Link The NT link has the following features.
• High-speed communications with specific types of PLCs can be executed.
The NT31/NT31C also supports OMRON’s high-speed 1:N NT Link.
• Writing in units of bits to the PLC memory area is possible.
This enables the other bits of words to which a touch switch has been al-
located to be allocated for other purposes (e.g. a lamp).
However, since data is written to the DM area in word units, the other bits
of words allocated to touch switches in this area cannot be used for other
purposes.
• The NT link can be used even when the PLC is in the RUN mode. (When
the host link method is used, the NT31/NT31C switches to the monitor
mode when the PLC is in the RUN mode.)
• In the case of PTs that support the standard 1:N NT Link (NT20S, NT31,
NT31C, NT600S, NT620S, NT620C, NT625C, NT631, NT631C) up to 8
PTs can be connected to one port of the PLC and used at the same time.
Up to 8 PTs (NT31, NT31C, NT631, and NT631C) can also be connected
simultaneously when the high-speed 1:N NT Link is being used.
All of the PTs connected to a PLC port must use either the standard or
high-speed 1:N NT Link; the two communications systems cannot share a
single port.
• When using a C200HX/HG/HE-(Z)E PLC and standard 1:N NT Links, up
to three 1:N NT Link systems (i.e., 24 PTs) can be connected by installing
a Communications Board in the option slot of the CPU Unit. (Only the
standard 1:N NT Link can be used.) For details on the Communications
Board, refer to the SYSMAC Communications Board Operation Manual
(W304-E1-@).
• When using a CQM1H PLC and standard 1:N NT Links, multiple 1:N NT
Link systems can be connected by installing Serial Communications
Boards in the Inner Board slots. For details on the Serial Communications
Board, refer to the CQM1H Serial Communications Board Operation Man-
ual (W365-E1-@).
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