SEMI E84 — Carrier Handoff
SEMI E84 defines the parallel I/O handshake used during automated carrier load and unload operations between active AMHS equipment and passive equipment such as a process-tool load port.
Area
AMHS
Profile coverage
300 mm Overhead Automation
Purpose
E84 coordinates the physical handoff locally, with defined signals, sequence expectations, timing, availability, and error behavior. It reduces ambiguity at the point where an OHT, AGV, or related system transfers a carrier.
Where it applies
Use E84 when the equipment and factory AMHS specification require its enhanced handoff interface. It is often deployed alongside GEM300 but is a separate real-time I/O interface, not a SECS/GEM message service.
Who implements it
The active transfer device and passive receiving equipment each implement their side of the handshake. The factory host does not drive every handoff signal; Tool Control Software and load-port I/O logic must coordinate modes, interlocks, sensors, and GEM-visible state.
Relationships and dependencies
- Operates beside, not inside, the E30/E37 SECS/GEM connection.
- Physical carrier state should agree with E87 carrier and load-port state.
- Commonly connects process equipment with transport systems described by E82 or related AMHS models.
Practical implementation guidance
- Implement the sequence as a deterministic state machine with named timers and diagnosable transitions.
- Reconcile E84 signals with load-port sensors, safety interlocks, auto/manual mode, and carrier presence.
- Provide timestamped I/O traces for commissioning and intermittent handoff troubleshooting.
Common mistakes
- Attempting to trigger the entire handoff directly from a GEM host command.
- Reporting carrier presence from software state before physical sensors and E84 completion agree.
- Resetting an error without a defined recovery sequence for both active and passive sides.