Yokogawa ALF111-S01 FOUNDATION Fieldbus Communication Module

The Yokogawa ALF111-S01, also cataloged as the ALF111 FOUNDATION Fieldbus Communication Module, operates as a dedicated hardware component for Link Active Scheduler (LAS) management and H1 fieldbus segment distribution within distributed control system (DCS) platforms.

Suffix Breakdown & Model Matrix

The ALF111 series utilizes explicit engineering suffixes to define hardware builds and hardware style revisions. Below is the technical breakdown for the ALF111-S01 configuration:

• ALF111: Core base model designator for the FOUNDATION Fieldbus H1 communication module.
• -S: Standard type construction baseline for standard industrial enclosure installation.
• 0: Phase indicator slot mapping designator.
• 1: Style code indicating the physical hardware design revision or updated sub-component generation.

Hardware Specifications

Process Control System Specifications

• FOUNDATION Fieldbus / Profibus PA Connectivity Operating as a Link Active Scheduler (LAS) master node, the module maintains strict deterministic control over the 31.25 kbit/s H1 segment loop. It governs macrocycle execution timings, issues token passes to slave instruments, and transfers periodic process variables directly into the central DCS database for regulatory control loop synchronization.
• Deterministic Processor Offloading and Redundancy Pairing The module manages synchronous scheduled communications and asynchronous messaging internally, ensuring network traffic routines do not introduce execution jitter to the main controller processor. Dual-redundant pairing options support installing two ALF111 units in the same node slot layer to manage automatic bump-less transfer of the LAS roll during an active hardware fault.

Frequently Asked Questions

Q: What are the consequences if a module running as the active Link Active Scheduler (LAS) fails on the H1 loop?

A: If the primary ALF111-S01 fails in a non-redundant layout, a configured backup LAS device located directly on the field network segment detects the loss of the scheduling token and automatically assumes control of the macrocycle execution timing to prevent loss of process data.

Q: Can the ALF111-S01 directly power the 32 fieldbus transmitters connected to its H1 segment loop?

A: No. The communication module does not inject operating power into the signal lines. An external, dedicated fieldbus power supply paired with an impedance-matching fieldbus power conditioner must be installed on the H1 network segment to drive connected transmitters and valves.