Omron CJ - REFERENCE MANUAL 10-2009 Reference Manual page 184

3. Instructions
UP/DOWN
Instruction
CONDITION ON
CONDITION OFF
Symbol
Applicable Program Areas
Function block
Area
definitions
Usage OK
Flags
There are no flags affected by UP(521) and DOWN(522).
Function
UP
UP(521) is placed between an execution condition and another instruction to turn the execution condition into
an up-differentiated condition. UP(521) causes the connecting instruction to be executed just once when the
execution condition goes from OFF to ON.
DOWN
DOWN(522) is placed between an execution condition and another instruction to turn the execution condition
into a down-differentiated condition. DOWN(522) causes the connecting instruction to be executed just once
when the execution condition goes from ON to OFF.
Hint
• The DIFU(013) and DIFD(014) instructions can also be used for the same purpose, but they require
work bits. UP(521) and DOWN(522) simplify programming by reducing the number of work bits and
program addresses needed.
Precautions
• UP(521) and DOWN(522) are intermediate instructions, i.e., they cannot be used as right-hand
instructions. Be sure to program a right-hand instruction after UP(521) or DOWN(522).
• The operation of UP(521) and DOWN(522) depends on the execution condition for the instruction as
well as the execution condition for the program section when it is programmed in an interlocked
program section, a jumped program section, or a subroutine.
Note Observe the following precaution when using UP(521) in a function block definition.
• The operation of UP(521) and DOWN(522) will not be consistent if the same function block instance
is executed more than once in the same cycle.
• An instance will not be executed while EN is OFF. Caution is thus required when using UP(521) and
DOWN(522) in a function block definition. For details, refer to information on restrictions on using
ladder programming instructions in the CX-Programmer Operation Manual: Function Blocks.
146
Mnemonic Variations
UP ---
DOWN ---
UP
UP(521)
Block program areas Step program areas
OK OK
Function
code
UP(521) turns ON the execution condition for the
521 next instruction for one cycle when the execution
condition it receives goes from OFF to ON.
DOWN(522) turns ON the execution condition for
522 the next instruction for one cycle when the execu-
tion condition it receives goes from ON to OFF.
DOWN
DOWN(522)
Subroutines Interrupt tasks
OK OK
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Function
SFC action or
transition programs
OK