Omron CJ - PROGRAMMING MANUAL 08-2008 Programming Manual page 323

Index Registers
Pointer address
(The above diagram shows
the status of the pointer
data before data is added.)
A
Pointer address
A
Stack
region
Note Actually, the first two words of the stack contain the PLC memory address of
the last word in the stack and the next word contains the stack pointer.
FIFO (First-in First-out) Processing
The following diagram shows the operation of a first-in first-out (FIFO) stack.
Pointer address
A
B
C
X
LIFO (Last-in First-out) Processing
The following diagram shows the operation of a last-in first-out (LIFO) stack.
Pointer address
1
Manipulating Specific Table Data
Individual entries in a table can be read, writing, inserted, or deleted. The fol-
lowing diagram shows an example for reading.
Pointer address
A
B
V
W
−n
X
An offset from the point
address is specified.
B
Pointer address
A
B
A
A
B
X
V
W
X
Read
V
Section 6-2
C
Pointer address
A
B
C
Reads the oldest word of data stored in
the stack. Each time that a word is read,
the pointer is decremented by one to
indicate the next address for storage.
Reads most recent word of data stored
in the stack. Each time that a word is
read, the pointer is decremented by one
to indicate the next address for storage.
Data at the position that was read
remains unchanged.
Data is read from a specific offset from
the point address in the table.
Manipulating specific table data can be
used, for example, in tracing items on a
conveyor.
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