ao_modbus_server

Active object handling Modbus RTU request and response event flows.

Inherited Component

Inherited Requirements

Relationship Diagram

UML class diagram for ao_modbus_server

SW Unit Relations

Outgoing Relations

Relation

UML Type

Visibility

Target Unit

Description

SWR-018

dependency

private

hal_event_adapter

Modbus server uses hardware-adapted UART events.

SWR-020

dependency

private

ao_config_manager

Modbus server forwards configuration update requests to config manager for validation and commit.

Incoming Relations

Relation

UML Type

Visibility

Source Unit

Description

SWR-011

dependency

public

ao_runtime_supervisor

Runtime supervisor dispatches communication events.

Data Types

ao_modbus_server_contextstruct

Internal runtime context for ao_modbus_server.

Struct Members

Name

Type

Description

session_state

uint8_t

Modbus session state.

last_function_code

uint8_t

Last processed function code.

exception_active

bool

Exception response active.

last_request_tick

uint32_t

Last request processing tick.
ao_modbus_server_eventstruct

Event payload handled by ao_modbus_server.

Struct Members

Name

Type

Description

signal_id

uint16_t

Modbus event signal id.

function_code

uint8_t

Requested function code.

register_address

uint16_t

Starting register address.

register_count

uint16_t

Register quantity.
ao_modbus_server_resultenum

Result code for ao_modbus_server operations.

Enum Members

Name

Value

Description

OK

0

Transaction served.

FRAME_ERROR

1

Frame parsing failed.

MODBUS_EXCEPTION

2

Exception response returned.

Attributes

Attribute

Type

Visibility

Description

ctx

ao_modbus_server_context

private

Runtime context for ao_modbus_server state timing and error tracking.

Methods

dispatch

  • Return Type: ao_modbus_server_result

  • Visibility: public

  • Description: Process one ao_modbus_server event and update runtime outputs.

Parameters

Name

Type

Direction

Description

event

ao_modbus_server_event

in

Process one ao_modbus_server event and update runtime outputs.

init

  • Return Type: ao_modbus_server_result

  • Visibility: public

  • Description: Initialize ao_modbus_server runtime state and dependencies.

Dynamic Behaviour

State Machines

ao_modbus_server_state

@startuml hide empty description [*] --> Comms_Init Comms_Init --> Idle : EVT_INIT_DONE Idle --> Rx_Frame : EVT_FRAME_RX Rx_Frame --> Validate : EVT_FRAME_COMPLETE Validate --> Respond : EVT_REQ_VALID Validate --> Error : EVT_REQ_INVALID Validate --> Error : EVT_CRC_FAIL Respond : do / build_modbus_response() Respond --> Idle : EVT_TX_DONE Error : do / send_exception_response() Error --> Idle : EVT_TX_DONE Error --> Idle : EVT_TIMEOUT @enduml

This state machine models Modbus request processing phases including frame reception validation protocol error handling and response transmission to ensure deterministic interface behavior for valid and invalid master transactions.

Sequence Diagrams

SEQ-001_Runtime_Event_Orchestration

@startuml hide footbox title Runtime Event Orchestration participant ao_runtime_supervisor participant evt_timer_service participant evt_dispatcher participant ao_monitoring participant ao_control participant ao_safety participant ao_diagnostics participant ao_modbus_server ao_runtime_supervisor -> evt_timer_service : init periodic tick ao_runtime_supervisor -> evt_dispatcher : init event loop loop each scheduler tick evt_timer_service -> ao_runtime_supervisor : tick event ao_runtime_supervisor -> evt_dispatcher : dispatch cycle evt_dispatcher -> ao_monitoring : monitor_event evt_dispatcher -> ao_control : control_event evt_dispatcher -> ao_safety : safety_event evt_dispatcher -> ao_diagnostics : diagnostics_event evt_dispatcher -> ao_modbus_server : comms_event end @enduml

Primary runtime interoperability sequence showing scheduler tick propagation through dispatcher fan-out and deterministic active-object processing order across monitoring control safety diagnostics and communication units.

SEQ-004_Modbus_Event_Servicing

@startuml hide footbox title Modbus Server Event Servicing participant ao_runtime_supervisor participant ao_modbus_server participant hal_event_adapter ao_runtime_supervisor -> ao_modbus_server : dispatch comms_event ao_modbus_server -> hal_event_adapter : request UART I/O hal_event_adapter --> ao_modbus_server : uart_rx/tx completion ao_modbus_server -> hal_event_adapter : publish protocol response @enduml

Runtime-driven communication events are processed by the Modbus server through hardware-adapted UART event exchange.

SEQ-005_Startup_To_Ready

@startuml hide footbox participant ao_runtime_supervisor participant evt_timer_service participant evt_dispatcher participant ao_monitoring participant ao_control participant ao_safety participant ao_diagnostics participant ao_modbus_server ao_runtime_supervisor -> evt_timer_service : init() ao_runtime_supervisor -> evt_dispatcher : init() ao_runtime_supervisor -> ao_monitoring : init() ao_runtime_supervisor -> ao_control : init() ao_runtime_supervisor -> ao_safety : init() ao_runtime_supervisor -> ao_diagnostics : init() ao_runtime_supervisor -> ao_modbus_server : init() group readiness gates evt_timer_service --> ao_runtime_supervisor : EVT_TIMER_READY evt_dispatcher --> ao_runtime_supervisor : EVT_DISPATCH_READY ao_monitoring --> ao_runtime_supervisor : EVT_AO_READY ao_control --> ao_runtime_supervisor : EVT_AO_READY ao_safety --> ao_runtime_supervisor : EVT_AO_READY ao_diagnostics --> ao_runtime_supervisor : EVT_AO_READY ao_modbus_server --> ao_runtime_supervisor : EVT_AO_READY end ao_runtime_supervisor -> evt_dispatcher : EVT_INIT_OK / start Run @enduml

Startup lifecycle sequence with explicit readiness gates before entering Run state.

SEQ-007_Controlled_Shutdown

@startuml hide footbox participant ao_runtime_supervisor participant evt_dispatcher participant ao_control participant ao_safety participant ao_diagnostics participant ao_modbus_server ao_runtime_supervisor -> evt_dispatcher : EVT_SHUTDOWN_REQ ao_runtime_supervisor -> ao_control : stop outputs to safe state ao_runtime_supervisor -> ao_safety : keep protective policy active ao_runtime_supervisor -> ao_diagnostics : publish shutdown status ao_runtime_supervisor -> ao_modbus_server : stop comm servicing ao_modbus_server --> ao_runtime_supervisor : EVT_STOPPED ao_diagnostics --> ao_runtime_supervisor : EVT_STOPPED ao_safety --> ao_runtime_supervisor : EVT_STOPPED ao_control --> ao_runtime_supervisor : EVT_STOPPED evt_dispatcher --> ao_runtime_supervisor : EVT_STOPPED ao_runtime_supervisor -> ao_runtime_supervisor : EVT_ALL_STOPPED / Shutdown complete @enduml

Controlled shutdown sequence defining stop ordering and completion criteria.