Memory Tables And Bar Graphs - Omron NT20S-ST121B-EV3 User Manual

Memory Tables and Bar Graphs

5-2

Memory Tables and Bar Graphs

Displaying and Referencing Character String Memory Table Contents
Since the character-string memory table entries can be allocated to the words
in the PLC, the PLC can write data to the character-string memory table
entries or the initial values can be set when creating the screen data.
Automatic updating is performed to ensure that the currently displayed NT20
character string memory table contents and PLC word contents always match
each other.
There are two methods for referencing character string memory table entries
used for character string display, as follows:
• Direct specification
• Indirect specification
• Direct Specification
Direct specification is a method of specification in which the contents of
displayed memory table entries are directly correlated with the contents of
the allocated words.
NT20
Direct
specification
a b c d
• Indirect Specification (Direct Connection Only)
In indirect specification, even if the displayed data is a character string, the
display is correlated with a numeral memory table entry. The contents (nu-
merical value) of this numeral memory table entry are regarded as a char-
acter string memory table entry number and the contents of the table entry
with this number is displayed.
Up to 50 numeral displays and 50 character string displays can be speci-
fied on one screen by using indirect specification.
NT20
Indirect
specification
a b c d
This specification method is a little complex, but it allows the display to be
changed more easily according to the circumstances. In the example above, if
1 were added to the contents of memory table entry 20 to give 52, the con-
tents of memory table entry 52 would be displayed instead.
The memory table entries used for display can also be allocated to areas in
the PLC, so that the display can also be changed in response to changes in
the data to be displayed (i.e., the contents of character string memory table
entry 51 in the example above).
However, in comparison with direct specification, indirect specification
requires more time for processing.
Allocated words
Character string
(character string memory table entry 51)
memory table entry 51
a b c d
Numeral memory
Allocated word (numeral memory table entry 20)
table entry 20
0 0 5 1
Character string Allocated words (character string table entry 51)
memory table entry 51
a b c d
Section 5-2
PLC
DM0100
6 1 6 2
6 3 6 4
PLC
DM0000
0 0 5 1
DM0100
6 1 6 2
6 3 6 4
177