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What is the most powerful PLC instruction
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What instruction or concept is the most powerful
when programming any manufacturer's PLCs
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Many people will guess timers, counters,
or the set and reset bid instructions
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These are all great instructions, but the
one that is the most powerful is the indirect
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or pointer instruction. In PLC programming,
pointers, also called indirect addressing, store or
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retrieve memory addresses of data or instructions.
They are instrumental when dealing with
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large amounts of data or performing complex
calculations. Machine recipes, sequence control
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and storage of test results are just a few examples
where this powerful PLC instruction is used
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We will examine how indirect addressing works in
a click, do more, and productivity PLCs. You will
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discover how easily and powerful pointers are when
programming. Let's get started. Detailed information
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about this video can be found at ACCautomation.ca.
A link is included in the description below
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The website offers extensive links, references,
and coding samples, making it a one-stop shop
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for all your automation queries.acccautomation.ca. Powerful PLC Indirect, Pointer
Instruction The pointer instruction will give you flexibility when programming
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Previously, we discussed the five steps to PLC. program development. Using
a sequence table is an excellent method to determine the states of each
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input and output in the PLC as we program our
machine. The indirect address can take this sequence
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table and program it directly. The inputs are compared
to an input table. If equal, the output pointer
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will move the output table value to the physical outputs Pointers are increment and the sequence continues A comparison
instruction is used on the last step and if equal the pointers are reset sequencing the machine over again This powerful method
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will involve changing the input and output
tables to change the sequence of operations
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Troubleshooting is quickly done because the
pointers show you the table value versus the actual
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input values. Once we understand the basic
concept of this powerful instruction, we can also
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use it to store values from a test in a series of
registers in the PLC. This is especially useful
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when the test is quicker than the corresponding
communication method. Stored recipes in the PLC can also
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be utilized to run on a machine. The indirect
pointer will load or keep the corresponding recipe
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required in the machine. How many more examples
and applications can you think of using indirect
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pointers? Let me know in the comments
below. Click PLC Indirect Point
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The Click PLC supports indirect addressing,
which the manuals refer to as pointer addressing
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This method utilizes the DS registers as
the offset value and can be used with the DS
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DD, DF, D-H-D, XD, YD, T-D, T-TD, and
TXT data register memory types. Example
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DD, DS3, this will point to the address
in DD that the DS3 value contains
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If DS3 has a 145 value, the address will use DD-145. As we
change DS3, DD's corresponding address will also change
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We can copy values to that location, logging,
and read values from that location, retrieving
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The corresponding post for this video provides
additional examples of indirect pointing
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See the link below. Productivity PLC Indirect Pointer We use arrays to handle indirect addressing in the Productivity
Series PLC A tag name can be specified as the index of the array Example Widget progress pointer a 1D array
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Widget progress, pointer underscore row, pointer underscore column, 2D array.
Individual elements, values in the array, are addressed by their index
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Coordinates, row, column, the address of the above elements
in the array called widget progress is widget progress
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for 2. Format, array name, row, column. Note, the
row and column index always begin at 1. The above
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array example was a two-dimensional array. 2D, X
and Y, the Productivity Series PLC can also have a
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one-dimensional array. 1D.X. Since we have only
one row in this array, we would address the element
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by the column location. In our example, widget
progress, 2, would be the location of the element
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highlighted. Format, array name, column. See the
links to the website below to discover more about
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the productivity series of PLCs. Do more, BRX, PLC
Indirect Pointer. Indirect Addressing allows an
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instruction's memory address to be varied when
running to point to multiple locations. All of the
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data blocks in the CPU can be used as arrays. This
includes the ones that you can define yourself
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The array index must be in the range of 0 to
65535 and must be stored in the VM memory location
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Example. In this example, we use V0 as the
pointer in the array. Its value ranges from 1 to 6
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We are using the instruction move V, V0, to V100. Several
examples are shown in the post on the website for this video
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Please see the links below Indirect addressing or pointer instruction is the most powerful instruction in PLC programming It stores or retrieves
memory addresses of data or instructions which is extremely useful when dealing with large amounts of data or performing complex calculations
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Pointers provide programming flexibility and can be used for
machine recipes, sequence control, and storage of test results
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They can be easily implemented in
Click, Do More, and Productivity PLCs
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indirect addressing can take a sequence table and program it directly, comparing
inputs to an input table and moving output table values to physical outputs
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This method involves changing input and output
tables to change the sequence of operations
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Troubleshooting is made easy because pointers
show table values versus actual input values
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Indirect addressing can also be used to store values
from a test in a series of registers in the PLC
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and to run stored recipes in a machine. If you
enjoyed this video, please hit the like button below
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If you have any questions about this video, please leave
a comment below, and I'll do my best to answer them
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I'll see you next time. Stay safe. You know
