Omron SYSMAC CS Series Instruction & Reference Manual page 101

Note Observe the following precaution when using UP(521) and DOWN(522) in a subroutine.
• The operation of UP(521) and DOWN(522) will not be consistent if the same subroutine is executed
more than once in the same cycle.
• An subroutine will not be executed while the input condition for the subroutine is OFF. Caution is thus
required when using UP(521) and DOWN(522) in a function block definition. For details, refer to
information on SBS(091).
• The CPU Unit performs logic operations between logic blocks. When you use the UP or DOWN
instruction and there are multiple input instructions between the left bus bar and the UP or DOWN
instruction, create the rung so that the signal flow (i.e., the power flow) goes from left to right on the
ladder diagram.
• The UP or DOWN instruction takes the previous execution result as the input signal and detects
when the signal turns ON or turns OFF (upward or downward differentiation). If either of these
instructions is used for a logic block, upward or downward differentiation is performed for the range of
the logic block.
Example Programming
 UP
0.00
 DOWN
0.00
CS/CJ/NSJ Series Instructions Reference Manual (W474)
i
0.01
When CIO 0.00 goes from OFF to ON, CIO
0.01 is turned ON for just one cycle.
0.00
0.01
Cycle
time
i
0.01
When CIO 0.00 goes from ON to OFF, CIO
0.01 is turned ON for just one cycle.
0.00
0.01
3. Instructions
Cycle
time
3
67