SEMI E5 — SECS-II
SEMI E5 defines SECS-II message structure, data item formats, streams, and functions used by intelligent manufacturing equipment and factory hosts. It is the common message language beneath GEM and GEM300.
Area
Communications
Profile coverage
200 mm Tool Standards · 300 mm Tool Standards · 300 mm Overhead Automation
Purpose
E5 gives equipment and host software a shared representation for messages and typed data. It separates message content from the transport, allowing the same SECS-II model to travel over legacy SECS-I or modern HSMS connections.
Where it applies
E5 applies whenever an interface exchanges SECS-II messages, regardless of wafer size. It is foundational for GEM, GEM300, and many equipment-specific models, but an E5 message library alone does not make an interface GEM compliant.
Who implements it
Both host and equipment must encode, decode, validate, and interpret the same message and data-item shapes. The equipment application must also connect each supported message to real state, commands, alarms, events, recipes, and material behavior.
Relationships and dependencies
- Runs over SEMI E4 SECS-I or SEMI E37 HSMS transport.
- Provides the message vocabulary used by SEMI E30 GEM.
- Carries services introduced by GEM300 standards such as E39, E40, E87, E90, and E94.
Practical implementation guidance
- Use strongly validated message definitions and preserve SECS numeric widths, list shape, and binary values.
- Reject malformed messages with documented behavior instead of silently coercing incompatible values.
- Test both encoded bytes and application semantics with representative host traffic.
Common mistakes
- Confusing a valid SECS-II encoding with correct GEM behavior.
- Flattening nested lists or narrowing U4, I8, U8, F4, and F8 values into incompatible application types.
- Implementing only successful request paths while omitting error, timeout, and unknown-message handling.