Host Link; Nt Link - Omron NT31 Setup Manual

Communications with the Host
Features of the Direct
Connection Function
1-4-2

Host Link

1-4-3

NT Link

The NT31/NT31C can directly write to and read from such allocated bits and
words to change the display status of the elements on the PT screen, control
the PT operating status, and notify the host of the status.
This function, which directly reads and writes the statuses of words and bits
without using a PLC program is called the direct connection function.
The words and bits allocated for direct connection are called the allocated
words and allocated bits.
The direct connection function allows the data to be displayed at the NT31/
NT31C to be read from the memory area in the PLC and written to memory
tables in the NT31/NT31C. Also, the data input at the NT31/NT31C can be
written to the memory area in the PLC. The NT31/NT31C screen can be
changed in accordance with statuses in the PLC memory area, and the NT31/
NT31C's status data can be written to the PLC's memory area.
NT31/NT31C
The direct connection function has the following features.
• The bits and words referring to operating status and work instruction infor-
mation and those for storing input data can be freely allocated to almost
any area of the PLC memory.
• Since the NT31/NT31C can directly refer to PLC bit and word data without
using the program at the PLC, it can be connected to the PLC without
changing the PLC program which controls the currently running produc-
tion line.
• The area to control and provide notification of NT31/NT31C status, includ-
ing display screens, display/no display status, and buzzer output, can be
freely allocated to any part of the PLC data area. This means that the
PLC status can be read and controlled just by reading this area at the
PLC side, without preparing a special communications program.
The direct connection function allows the NT31/NT31C to directly read and
write almost all bits and words in the PLC and to automatically change the
NT31/NT31C screen display. This function can reduce the load on the PLC so
that its program development efficiency is improved.
The host is connected to a PT in a 1:1 connection, and the words and bits of
the host are read and displayed by host link communications. This method
can be used for connection to the majority of PLC types.
NT link is a method for high-speed communications with a PLC using the
direct connection function. The PLCs that can be connected with the NT link
are as follows.
• When using the built-in host link function of a CPU Unit or SRM1:
CPM1, CPM2A, CPM2C, CQM1, CQM1H, C200HS, C200HX/HG/HE(-
Z)E, CS1G/CS1H-E(V1), CS1D, CJ1G/CJ1H/CJ1M, CVM1/CV-series
PLC (-EV1 or later version), SRM1
PLC
I/O relay area
DM area
Auxiliary relay area Timers/counters
Section 1-4
17