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2-12
Section
Inputting Numeric Values
198
value in the numeral memory table changes.
Reference:
When the Storage Type is BCD, the numeral memory table’s signed binary data
is converted to data for storage in the host word (BCD data) and written to the
host. If the value is negative the most significant digit in the word is set as F. This
means that the maximum number of digits for a negative number (integer part +
decimal fraction part) is seven.
When the Storage Type is Binary, the contents of the numeral memory table are
written without alteration to the host word.
However, when a negative number is written to a numeral memory table whose
number of allocated words at the host is one, it is stored immediately after input
as a 16-bit negative number.
The data is stored in the numeral memory table as a 32-bit negative number in
this case as well.
Upper/Lower (Max./Min.) Limit Check
The PT has a function to check the correctness of an input numeric value to pre-
vent a numeric value outside the allowable range from being input so that the
input of an illegal value will not adversely affect the system.
The upper/lower (max./min.) limit check is executed in the timing indicated be-
low according to the type of a numeral setting input field.
For a thumbwheel type numeral setting input field, the check is executed each
time the increment/decrement key of each digit position is pressed.
With a thumbwheel type numeral setting input field, if n...n < m...m [upper limit:
1n...n, lower limit: 0m...m (n and m are arbitrary values at each digit)], carry over
and underflow are not possible at the highest digit position.
Example:
If the upper limit value and the lower limit value are 1200 and 201, respectively,
the numeric value can be changed only in the following range: from 201 to 999 if
an initial value is a 3-digit value and from 1000 to 1200 if an initial value is a 4-digit
value.
The reason for this is that the upper/lower (max./min.) limit check function does
not allow the numeric value at the highest digit position to change from 0 to 1 or
from 1 to 0.
To avoid this, set the upper and lower limit values so that n...n
y
m...m, or pro-
vide a touch switch separately to write a numeric value for carry over or under-
flow.
Note
When the numeral values entered are confirmed, upper/lower limits are
checked.
Reference:
Since values input at the PT are handled as signed binary data, be sure to ob-
serve the following upper/lower limit settings at the Support Tool when numbers
are being input in hexadecimal with its unlimited input range.
•
The following values are recognized internally in the PT.
1 word:
8000
H
↔
0000
H
↔
7FFF
H
(–32,768
↔
0
↔
32,767 decimal)
2 words: 8000 0000
H
↔
0000 0000
H
↔
7FFF FFFF
H
(–2,147,483,648
↔
0
↔
2,147,483,647 decimal)
•
In the Support Tool, the upper/lower limits are set in decimal. (The $ prefix can
be added to input hexadecimal values.
Using the figures above, the following table shows the upper/lower limits to be
set at the Support Tool.
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Summary of Contents for NT21 Series
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