Guidelines for SCMD instructions

Guidelines for SCMD instructions

Keep these guidelines in mind when using the
Equipment Sequence
 Command (SCMD) instruction. The SCMD instruction can send these commands: START, RESTART, HOLD, STOP, ABORT, and RESET.
Guideline
Details
Limit execution of the SCMD instruction to a single scan.
Limit the execution of the SCMD instruction to a single scan. Each command applies to only a specific state or states. Once the
Equipment Sequence
 changes state, the command is no longer valid. To limit execution, use methods such as:
  • Run the SCMD instruction within a P1 Pulse (Rising Edge) or P0 Pulse (Falling Edge) action.
  • Place a one-shot instruction before the SCMD instruction.
  • Run the SCMD instruction and then advance to the next step.
The
Equipment Sequence
 must be owned by the program to command it.
Both
Equipment Sequence
s and
Equipment Phase
s must be
owned
to be commanded. The ownership commands are
Attach
(SATT)
and
Detach
(SDET).
Internal sequencers (programs), external sequencers (
FactoryTalk Batch
), and operators use an
Attach
 instruction to command an
Equipment Sequence
.
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