SEMI E4 — SECS-I
SEMI E4 defines the legacy serial transport used to move SECS messages between equipment and a factory host. It remains relevant when modernizing installed tools that still communicate through an RS-232-class link.
Area
Communications
Profile coverage
200 mm Tool Standards
Purpose
E4 addresses message transfer rather than message meaning. It defines how a serial connection frames, exchanges, acknowledges, retries, and recovers SECS traffic so both endpoints can reliably move the messages whose content is defined by E5.
Where it applies
Use E4 when a customer or installed equipment interface specifically requires SECS-I. New Ethernet-connected implementations normally use E37 HSMS instead. Wafer diameter alone does not select the transport; the actual host interface specification does.
Who implements it
The equipment communication endpoint and the host endpoint both implement the serial protocol. Tool Control Software normally owns the equipment-side state machine, timers, retries, and mapping between received blocks and complete SECS-II messages.
Relationships and dependencies
- Carries the message structures defined by SEMI E5.
- Is the legacy transport alternative to SEMI E37 HSMS.
- Can support a GEM interface when the factory still requires serial communications.
Practical implementation guidance
- Treat serial framing, block numbering, timers, retries, and duplicate detection as one tested protocol component.
- Capture wire-level diagnostics so field engineers can distinguish transport faults from SECS-II content faults.
- Confirm cable, port, baud, parity, timeout, and host expectations during integration planning.
Common mistakes
- Calling an interface SECS-I when it only implements a proprietary serial message format.
- Mixing transport retry behavior with application-level message handling.
- Assuming a serial retrofit can be replaced by HSMS without coordinating the factory host change.