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ZPLC Runtime Engine

The ZPLC internal runtime is the execution core of the platform. Designed specifically for deterministic performance on embedded systems, it safely executes .zplc bytecode, manages memory, schedules automation tasks, and integrates with platform-specific hardware.

Core Responsibilities​

The ZPLC runtime provides a comprehensive virtual environment tailored for IEC 61131-3 task execution. Its responsibilities include:

  • Loading .zplc bytecode programs and their metadata.
  • Instantiating Virtual Machines (VMs) with isolated execution contexts.
  • Enforcing structural memory boundaries (Process Images, internal Work memory, retained data).
  • Scheduling and orchestrating Cyclic/Event-based PLC tasks.
  • Yielding physical I/O, networking, and storage operations to the underlying Hardware Abstraction Layer (HAL).

Subsystem Architecture​

Shared Memory Model​

To guarantee both safety and performance in resource-constrained ICs, the ZPLC Runtime Memory Contract defines strict bounds for runtime elements:

  • IPI (Input Process Image): Isolated memory mapped buffer for safe physical input reading.
  • OPI (Output Process Image): Buffer mapping logic results to hardware outputs.
  • Work Memory: Dynamic volatile execution stack allocated during runtime execution.
  • Retain Memory: Persisted state memory (non-volatile) tracking block metadata and RETAIN values.

Target Portability​

By ensuring that the internal runtime delegates bare-metal concerns to a strictly defined HAL, ZPLC easily runs on multiple architectures:

  • Zephyr RTOS: The primary execution platform for hardware edge controllers. Runs the firmware app natively on bare-metal hardware.
  • Host Native Simulation: Provides SoftPLC desktop simulation by adapting HAL primitives natively mapping to Windows, macOS, or Linux filesystems and processes.