Omron SYSMAC CJ - REFERENCE MANUAL 08-2008 Reference Manual page 751

Table Data Processing Instructions
Description
Flags
Precautions
Area
Data Registers
Index Registers
Indirect addressing
using Index Registers
FIFO(633) reads the oldest word of data from the stack (TB+4) and outputs
that data to D. Next, the stack pointer (TB+3 and TB+2) is decremented by
one, all of the remaining data in the stack is shifted downward by one word,
and the data read from TB+4 is deleted. The data at the end of the stack (the
address that was indicated by the stack pointer) is left unchanged.
TB
Stack TB+1
pointer
TB+2
TB+3
TB+4
First-in first-out
Use FIFO(633) in combination with PUSH(632). After PUSH(632) has been
used to write data into a stack, FIFO(633) can be used to read data from the
stack on a first-in first-out basis.
FIFO(633) reads the beginning data from the stack and deletes this data to
move the next one forward.
Name Label
Error Flag ER
The stack must be defined in advance with SSET(630).
TB
---
---
,IR0 to ,IR15
–2048 to +2047 ,IR0 to –2048 to +2047 ,IR15
DR0 to DR15, IR0 to IR15
,IR0+(++) to ,IR15+(++)
,–(– –)IR0 to, –(– –)IR15
PC memory
address
TB
Oldest
TB+1
data
TB+2
TB+3
TB+4
Stack
pointer
Operation
ON if the contents of the stack pointer (TB+3 and TB+2) is
less than or equal to the PLC memory address of first
word in the data region of the stack (TB+4).
(This is a stack underflow error.)
OFF in all other cases.
Section 3-17
D
DR0 to DR15
PC memory
address
m–1
m–1
711