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Direct Connection Function
Section 1-4
1-4 Direct Connection Function
The communication method applied between the NT20S-ST121-EV3 and the PC
is either a host link or NT link. To connect an NT20S-ST122-V1 and PC, the C200H
direct communication function is used.
The following describes the “direct connection” function available with the
NT20S-ST121-EV3/ST122-V1, and communication with a PC.
' The NT20S-ST128 uses an RS-232C interface for communication with the PC
(refer to Section “Communications by RS-232C”).
The NT20S can be used to refer to the contents necessary for the display informa-
tion or to allocate the bits and words used for storing the input data to any area in
the PC. The NT20S can directly write and read such allocated bits and words so as
to change the display elements, control the operating status, and notify the status.
This function is called the “direct connection function”. The NT20S-ST121-EV3/
ST122-V1 is designed exclusively for use with the direct connection.
The bits and words allocated by the direct connection function are called “allocated
bit” and “allocated word” respectively.
This function allows to read the information to be displayed on the NT20S from the
memory area in the PC and to write it to the memory table in the NT20S. Also, the
data input on the NT20S can be written to the PC’s memory area. The NT20S
screen status can be switched according to the PC’s memory area, and the
NT20S’s status data can be written to the PC’s memory area.
' The NT20S-ST121-EV3 can only communicate with a PC that supports the
host link or NT link function. The NT20S-ST122-V1 can only communicate with
PCs that support the C200H direct communication function.
NT20S PC
DM area Internal relay area
Auxiliary relay area
Timer/counter
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