Transcript
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
Objectives
• Use PLC instructions for moving data from one register to another.
• Create stacks for storing and retrieving data from PLC memory.
• Move data between tables.• Use PLC instructions for number system
conversion.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
Data Handling Instructions
• Reading, storing, retrieving, and writing of data on ports and registers.
• Moving or copying data to another register or file.
• Converting data to a different number system.
• Performing a logic operation on data.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
Data Handling Instructions (Cont.)
• Move (MOV).• Masked move
(MVM).• FIFO load (FIFO).• FIFO unload (FFU).• LIFO load (LIFO).• LIFO unload (LFU).• Copy file (COP).• Fill file (FLL).
• Convert to BCD (TOD).• Convert from BCD
(FRD).• Convert from radians to
degrees (DEG).• Convert from degrees
to radians (RAD).
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
Index Register
• Sometimes simply called a pointer.• A register that holds an address of a
data. • Used to move a word into a specific
address.• Data is placed in another data register.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO
• Like pallets, data registers can be stored and retrieved in two different ways:– First-in-first-out (FIFO).– Last-in-first-out (LIFO).
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
• Concept of storing and retrieving pallets is similar to the way data is placed in and retrieved from a stack.
• A stack in PLC or computer terms:– A group of consecutive data registers, or
words, placed temporarily in a memory location, or buffer.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
• When stacking data: – Stack grows larger as data registers are
placed in stack.– Stack grows smaller as data registers are
retrieved from stack.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
• In FIFO operation, first item in stack is first item out of stack.
• In LIFO operation, last item in stack is first item out of stack.
• Push operation – placing an item in a stack.
• Pop operation – retrieving an item from a stack.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
• Allen-Bradley SLC 500 PLCs have four instructions for LIFO and FIFO operations:– FIFO load (FFL).– FIFO unload (FFU).– LIFO load (LFL).– LIFO unload (LFU).
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FIFO and LIFO (Cont.)
• In PLC systems, stacks are created when stacks of integer words (i.e., double-byte data) are stored in the memory buffer.
• Data can be transferred into a register or another memory location from the stack.
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
FFL Load Instruction
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
LFL Load Instruction
Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.
Copy File and Fill File Instructions
• Data handling instructions used to store blocks of data in a PLC file:– Copy file (COP).– Fill file (FLL).
• Can use these instructions to manually enter a file with constant numbers or data from another file.
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