Omron SYSMAC CJ - REFERENCE MANUAL 08-2008 Reference Manual page 951

Step Instructions
1,2,3...
The step programming area is from the first STEP(008) instruction (which
always takes a control bit) to the last STEP(008) instruction (which never
takes a control bit).
Starting Step Execution
SNXT(009) is placed at the beginning of the step programming area to start
step execution. It turns ON the control bit specified for B for the next
STEP(008) and proceeds to step B (all instructions after STEP(008) B). A dif-
ferentiated execution condition must be used for the SNXT(009) instruction
that starts step programming area execution, or step execution will last for
only one cycle.
Proceeding to the Next Step
When SNXT(009) occurs in the middle of the step programming area, it is
used to proceed to the next step. It turns OFF the previous control bit and
turns ON the next control bit B, for the next step, thereby starting step B (all
instructions after STEP(008) B).
Ending the Step Programming Area
When SNXT(009) is placed at the very end of the step programming area, it
ends step execution and turns OFF the previous control bit. The control bit
specified for B is a dummy bit. This bit will however be turned ON, so be sure
to select a bit that will not cause problems.
STEP(008)
STEP(008) functionS in following 2 ways, depending on its position and
whether or not a control bit has been specified.
1. Starts a specific step.
2. Ends the step programming area (i.e., step execution).
Starting a Step
STEP(008) is placed at the beginning of each step with an operand, B, that
serves as the control bit for the step.
The control bit B will be turned ON by SNXT(009) and the instruction in the
step will be executed from the one immediately following STEP(008). A20012
(Step Flag) will also turn ON when execution of a step begins.
After the first cycle, step execution will continue until the conditions for chang-
ing the step are established, i.e., until the SNXT(009) instruction turns ON the
control bit in the next STEP(008).
When SNXT (009) turns ON the control bit for a step, the control bit B of the
current instruction will be reset (turned OFF) and the step controlled by bit B
will become interlocked.
Handling of outputs and instructions in a step will change according to the
ON/OFF status of the control bit B. (The status of the control bit is controlled
by SNXT(009)). When control bit B is turned OFF, the instructions in the step
are reset and are interlocked. Refer to the following tables.
Control bit status
ON
ON OFF
OFF
Handling
Instructions in the step are executed normally.
Bits and instructions in the step are interlocked
as shown in the next table.
All instructions in the step are processed as
NOPs.
Section 3-22
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