1-4SectionCommunications with the Host
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1-4 Communications with the Host
The NT21, NT31/NT31C, or NT631/NT631C is connected to the host by one of
the following four communication methods.
The following communications can be used to connect an OMRON PC:
• Host link
• 1:1 NT Link
• 1:N NT Link (standard or high-speed)
The following communications can be used to connect another companies’ PC:
• Communications protocol supported by the other company’s PC
(NT31/NT31C or NT631/NT631C only)
The following communications can be used to connect RS-232C/RS-422 de-
vices, such as factory computers:
• Memory links
In all of these communication methods that can be used with NT21,
NT31/NT31C, or NT631/NT631C, data communication with host is by direct
connection (Memory link is, however, a quasi-direct connection).
In the following, the host link and NT Link that carry out the direct connection will
be discussed. Memory link will be explained in section 1-5 Communication by
Memory Link.
1-4-1 Direct Connection Function
With the NT21, NT31/NT31C, or NT631/NT631C, the bits and words used to ac-
cess data required for display, and those for storing input data, can be allocated
in any part of the PC memory area.
The NT21, NT31/NT31C, or NT631/NT631C 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 statuses to the host.
This function, which directly reads and writes the statuses of words and bits with-
out using a PC 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 PT to be
read from the memory area in the PC and written to memory table entries in the
PT. Also, the data input at the PT can be written to the memory area in the PC.
The PT screen can be changed in accordance with statuses in the PC memory
area, and the PT’s status data can be written to the PC’s memory area.
PCPT
DM Area IR/CIO Area
AR Area Timer/Counter Area
The direct connection function has the following features.
• The bits and words used to access operating status and work instruction in-
formation and those for storing input data can be freely allocated in almost any
area of the PC memory.
• Since the PT can directly access PC bit and word data without using the pro-
gram at the PC, it can be connected to the PC without changing the PC pro-
gram that controls the currently running production line.
Features of the Direct
Connection Function
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