AutomationDirect DL205 Manual

DL205 Analog Manual, 7th Edition Rev. D
7-13
Chapter 7: F2-04THM, 4-Channel Thermocouple Input
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Writing the Control Program
Reading Values Pointer Method and Multiplexing
There are two methods of reading values:
• Pointer method
• Multiplexing
The multiplexing method must be used with 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 highly
recommended to use the pointer method.
Pointer Method for the DL240/250-1/260 CPUs
The CPU has special V-memory locations assigned to each base slot that greatly simplifies the
programming requirements. These V-memory locations:
• Specify the number of channels to scan.
• Specify the storage locations.
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 used. This is all
that is required to read the data into V-memory locations. Once the data is in V-memory, math
instructions can be used on the data, compare the data against preset values, etc. V2000 is used
in the example, but any user V-memory location can be used. The module is installed in slot 2
for the examples. Use the V-memory locations shown in the application. The pointer method
automatically converts values to BCD.
NOTE: DL240 CPUs with firmware release version 2.5 or later and DL250 CPUs with firmware release version 1.06 or later
support this method. Use the DL230 multiplexing example if the firmware revision is earlier.
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SP0
LD
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LDA
O2000
OUT
V7672
This loads an octalvalue forthe firstV-memorylocationthat will be
used to storethe inc oming data. Forexample, theO2000 entered
herewoulddesignate thefollowing addresses:
Ch1--V2000, V2001,Ch2-- V2002, V2003, Ch 3--V2004,V2005,
Ch 4--V2006, V2007.
Theoctal address(O2000)isstoredhere. V7672isassignedtoslot
2 and acts as a pointer,whichmeans theCPU will usethe octal
value in this location to determine exactlywheretostore the
incoming data.
OUT
V7662
Spec ial V-memory location assignedtoslot2that c ontains the
numberofchannelsto scan.
00
LD
Loadsaconstant that specifies the numberofchannelstoscan and
thedataformat.The upperbyte, most significant nibble (MSN)
selects the dataformat(0=BCD, 8=Binary),the LSNselects the
numberofchannels(1, 2, 3, or 4).
-or-
Thebinaryformatisusedfor displayingdataonsomeoperator
interfaces.The DL230/240 CPUs do notsupport binarymath
functions, whereasthe DL250 does.
04 K0084

AutomationDirect DL205 Specifications

General

Brand	AutomationDirect
Model	DL205
Category	Controller
Language	English