DL205 Analog Manual, 7th Edition Rev. D
6-15
Chapter 6: F2-04RTD 4-Channel RTD Input
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Negative Temperatures 2’s Complement for the DL240, DL250-1 and DL260
CPUs (Binary/Pointer Method)
The 2’s complement mode used for negative temperature display purposes, while at the
same time using the magnitude plus sign of the temperature in a control program. The
DirectSoft element Signed Decimal is used to display negative numbers in 2’s complement
form. To find the absolute value of a negative number in 2’s complement, invert the number
and add 1 as shown in the following example:
Understanding the Input Assignments (Multiplexing Ladder Only)
Remember that this module appears to the CPU as a 32-point discrete input module. Use
these points to obtain:
• An indication of which channel is active
• The digital representation of the analog signal
• Module diagnostic information
Since all input points are automatically mapped into V-memory, it is easy to determine the
location of the data word that will be assigned to the module.
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LD
V2000
OUT
V2010
ADDB
K1
V2000K8000
²
INV
Loadnegativevalue into theaccumulator so we
canconvertittoapositivevalue.
Invert thebinarypattern in theaccumulator.
Add1.
Save Channel1dataatV2010.
Repeatfor other channelsasrequired.
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