Omron NT21 User Manual

1-5SectionCommunication by Using Memory Links
35
1-5 Communication by Using Memory Links
In this section, a communication method other than the direct connection, called
the memory link, is discussed.
1-5-1 Memory Link
The memory link is a method to send and receive data between a personal com-
puter or a FA computer and the PT by using RS-232C/422A communication.
In memory link, there is an area called the PT Memory, as shown below, inside
the PT, and this area is treated as a virtual area on the PC. This allows PT
memory and the display elements of the PT to make a quasi-direct connection.
By sending a command for the memory link, the host can make the PT execute
processes through PT memory. Frequently used commands are kept handy for
read and write tasks of the numeral memory table, character-string memory
table, and bit memory table.
Lamp
PT memory
PT
RS-232C/422A
communication
PC
NT31/NT31C
Direct connection
Numeral
memory
table
In the memory link method, the only difference is that the PT finds its commu-
nication 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 NT21, NT31/NT31C,
and 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.
• The Programming Console and Device Monitor functions cannot be used.
• The following strobes of PT status notify bits do not turn ON (page 7 to 27).
Screen switching strobe
Numerals input strobe
Character-string input strobe
• The usable area for allocation is the PT memory only.
1-5-2 Comparison between Direct Connection and Memory Link
The major differences between the direct connection and the memory link are as
follows:
• In the memory link method, the communication with the host should be carried
out by using commands. Compared to the ordinal direct connection, which can
be used requiring almost no programs, the memory link method requires a pro-
gram that is necessary for interchange of commands. This, however, gives ad-
vantages to the memory link method by using a large variety of functions avail-
able in the direct connections from major models such as a personal computer
and a FA computer equipped with RS-232C/RS-422A communication means,
allowing the PT to be suited for larger usage.

Omron NT21 Specifications

General

Brand	Omron
Model	NT21
Category	Touch terminals
Language	English