Purpose
Deriving Manual Mode from the other operating-mode conditions ensures that the control program has a defined operating mode after leaving E-Stop Mode or Auto Mode. It also keeps mode selection separate from the commands that request individual machine actions.
The PLC Pro ensures that HMI clearly indicates when Manual Mode is active.
Derive Manual Mode from the Other Operating Modes
The PLC Pro establishes Manual Mode whenever the control program is not in E-Stop Mode and not in Auto Mode, as shown in Figure 1.
Manual Mode is never latched. When either E-Stop Mode or Auto Mode is active, Manual Mode is FALSE. When both are inactive, Manual Mode is TRUE.
Indicate Manual Mode via HMI
The HMI indication follows the same Manual Mode status used by the control program. The indicated status is not separately selected, latched, or inferred from any other condition.
A clear indication allows the operator to distinguish Manual Mode from E-Stop Mode and Auto Mode. It also establishes the operating context in which manual commands may be issued without implying that any particular command is permitted or that any action will be completed.
When the PLC Pro is included during the design phase, the preferred method is a typically green lighted pushbutton that requests transitions between Manual Mode and Auto Mode. The light indicates Auto Mode. When the light is off, the control program is in Manual Mode.
When the controls design provides a maintained “MANUAL/AUTO” selector switch, the PLC Pro uses the switch-arming method. After Auto Mode is cancelled, the switch must first be detected in the “MANUAL” position before returning it to the “AUTO” position can issue a new request for Auto Mode. The same arming pattern is illustrated for a maintained Manual Mode command in Emergency Stop Mode Recovery.
PLC Pro Design Rules
- Manual Mode is derived from E-Stop Mode and Auto Mode rather than separately latched or commanded.
- The HMI indication of Manual Mode follows the same status used by the control program.
- Entry into Manual Mode does not initiate motion, resume an interrupted action, or make a retained command effective.