# Error Codes

**Path**: [`src/modbus/error_codes.h`](../../src/modbus/error_codes.h)

**Revision History**: Initial documentation

A comprehensive collection of error codes used throughout the Modbus implementation. This header defines specific error code enumerations for different types of errors that can occur during Modbus operations.

## REQUIREMENTS

No specific hardware pins required. This is a pure software component providing error code definitions.

## PROVIDES

- `ModbusErrorCode` - Enumeration for general Modbus error codes
- `ModbusDeviceErrorCode` - Enumeration for device-specific Modbus error codes
- `ModbusExceptionCode` - Enumeration for standard Modbus exception codes

## FEATURES

- Standardized error code definitions for Modbus protocol implementation
- Clear separation between different categories of errors
- Compliance with standard Modbus exception codes
- Error codes to handle both protocol-level and device-specific errors

## DEPENDENCIES

None. This is a standalone header file defining error code enumerations.

```mermaid
graph TD
    ErrorCodes[Error Codes]
```

## BEHAVIOUR

The error codes are used to report and handle various error conditions throughout the Modbus implementation.

```mermaid
graph TD
    Start[Operation Start] --> Operation[Modbus Operation]
    Operation --> CheckError{Error?}
    CheckError -->|No| Success[Operation Successful]
    CheckError -->|Yes| Identify[Identify Error Type]
    Identify -->|Protocol Error| ProtocolError[ModbusErrorCode]
    Identify -->|Device Error| DeviceError[ModbusDeviceErrorCode]
    Identify -->|Exception| Exception[ModbusExceptionCode]
    ProtocolError --> Handle[Handle Error]
    DeviceError --> Handle
    Exception --> Handle
    Handle --> End[End Operation]
    Success --> End
```

## TODOS

### PERFORMANCE

- Consider optimizing error handling mechanisms for minimal runtime overhead

### SECURITY

- Review error codes to ensure they don't expose sensitive system information
- Consider adding error codes for security-related issues (authentication failures, access violations)

### COMPLIANCE

- Verify that all Modbus exception codes match the latest Modbus specification
- Consider adding compliance with IEC 61131-3 error handling recommendations

### RECOMMENDATIONS

- Use appropriate error codes consistently across the codebase
- Consider extending error codes with additional information for debugging purposes
- Implement comprehensive error logging using these error codes