HSMS (High-Speed SECS Message Services) is the TCP/IP-based communication protocol that replaced the original RS-232 SECS-I serial link for connecting semiconductor equipment to factory host systems. It's defined by SEMI standard E37.

Why HSMS Replaced SECS-I

Speed: SECS-I was limited to 9600 baud over serial cables. HSMS runs over Ethernet at 100Mbps to 1Gbps. Distance: Serial cables were limited to about 15 meters. TCP/IP works over any network distance. Multi-connection: HSMS supports multiple simultaneous connections while SECS-I was point-to-point only. Reliability: TCP/IP provides built-in error detection, retransmission, and flow control.

Connection Modes

Passive mode (most common in production): Equipment listens for incoming connections from the host. Active mode: Equipment initiates the connection to the host.

Message Types

• Data Message: Carries SECS-II messages (the actual process data, alarms, recipes) • Select Request/Response: Establishes communication session • Deselect: Closes session gracefully • Linktest: Heartbeat to verify connection is alive • Separate: Force-closes session

Typical Setup

Each tool has a unique IP address and port number. The host (MES/EI) connects to each tool individually. HSMS wraps SECS-II message content—the application-layer protocol (SECS-II) remains the same whether transported over SECS-I or HSMS.