DL205 Analog Manual, 7th Edition Rev. D
3-15
Chapter 3: F2-04AD-2, F2-04AD-2L, 4-Channel Analog Voltage Input
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Writing the Control Program
Reading Values: Pointer Method and Multiplexing
There are two methods of reading values:
• The pointer method
• Multiplexing
The multiplexing method must be used when using a DL230 CPU. The multiplexing method
must also be used with remote I/O modules (the pointer method will not work). Either method
can be used with the DL240, DL250-1 and DL260 CPUs, but for ease of programming it is
strongly recommended to use the pointer method.
Pointer Method for the DL240, DL250-1 and DL260 CPUs
The DL205 series has special V-memory locations assigned to each base slot that will greatly
simplify the programming requirements. These V-memory locations allow you to:
• specify the data format
• specify the number of channels to scan
• specify the storage locations
NOTE:
DL250 CPUs with firmware release version 1.06 or later support this method. If the DL230 example needs to be
used, module placement in the base is very important. Review the section earlier in this chapter for guidelines.
The example program shows how to setup these locations. Place this rung anywhere in the
ladder program, or in the initial stage if stage programming instructions are being used. This
is all that is required to read the data into V-memory locations. Once the data is in V-memory
math can be used on the data, compare the data against preset values, and so forth. V2000 is
used in the example but you can use any user V-memory location. In this example the module
is installed in slot 2. Be sure to use the V-memory locations for the module placement. The
pointer method automatically converts values to BCD (depending on the LD statement in the
ladder logic).
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SP0
LD
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LDA
O2000
OUT
V7672
This loads an octal value for the first V-memory location that will be
used to store the incoming data. For example, the O2000 entered
here would designate the following addresses.
Ch1 -- V2000, Ch2 -- V2001, Ch3 -- V2002, Ch 4 -- V2003
The octal address (O2000) is stored here. V7672 is assigned to slot
2 and acts as a pointer, which means the CPU will use the octal
value in this location to determine exactly where to store the
incoming data.
OUT
V7662
Special V-memory location assigned to slot 2 that contains the
number of channels to scan.
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LD
Loads a constant that specifies the number of channels to scan and
the data format. The upper byte, most significant nibble (MSN)
selects the data format (i.e. 0=BCD, 8=Binary), the LSN selects the
number of channels (i.e. 1, 2, 3, or 4).
- or -
The binary format is used for displaying data on some operator
interfaces. The DL230/240 CPUs do not support binary math
functions, whereas the DL250 does.
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K
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Содержание DL205
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