Omron CVM1D, Operation Manual

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STEP DEFINE: STEP(008)
(008)
STEP
B
B: Bit CIO, G, A
Operand Data Area Ladder Symbol
(008)
STEP
STEP START: SNXT(009)
(009)
SNXT
B
B: Bit CIO, G, A
Operand Data Area Ladder Symbol
STEP(008) uses a control bit to define the beginning of a section of the program
called a step. STEP(008) does not require an execution condition, i.e., its execu-
tion is controlled through the control bit.
To start step execution, SNXT(009) is used with the same control bit as used for
the first STEP(008). If SNXT(009) is executed with an ON execution condition,
the step with the same control bit is executed. If the execution condition is OFF,
the step is not executed. You must use a differentiated execution condition for
the SNXT(009) instruction that starts step execution or step execution will last
for only one cycle.
The SNXT(009) instruction must be written into the program before the program
reaches the step it starts. It can be used at different locations before the step to
control the step according to two different execution conditions (see example 2,
below). Any step in the program that has not been started with SNXT(009) will
not be executed.
Once SNXT(009) is used to start step execution, step execution will continue
until STEP(008) is executed without a control bit. STEP(008) executed without a
control bit is used to stop step execution and return to normal execution.
STEP(008) without a control bit must be preceded by SNXT(009) with a dummy
control bit. It cannot be a control bit used in a STEP(008).
Execution of a step is completed either by execution of the next SNXT(009) or by
turning OFF the control bit for the step (see example 3). When the step is com-
pleted, all I/O Area output bits, Work Area, Holding Area, and CPU Bus Link Area
bits in the step are turned OFF, Timers (except TTIM(120), TIML(121), and
MTIM(122)) in the step are reset to their SVs. Counters, shift registers, and bits
used in KEEP(011) maintain status.
Steps can be programmed consecutively. Each step must start with STEP(008)
and generally ends with SNXT(009) (see example 3, for an exception). All con-
trol bits must be in the same word and they must be consecutive.
When steps are programmed in series, three types of execution are possible:
sequential, branching, or parallel. The execution conditions for, and the position-
ing of, SNXT(009) determine how the steps are executed. The three examples
given later demonstrate these three types of step execution.
Description
STEP DEFINE and STEP START: STEP(008)/SNXT(009)
Section 5-29