AUTOSAR for dummies - #3.3 Services layer

The Service Layer is the highest layer of the Basic Software.The Services Layer offers Operating system services, Vehicle network communication and management services, Memory services, Diagnostic Services, ECU state management. Services could be broadly classified into 

• System services
• Communication services
• Memory services

System Service:

The System Services are a group of modules and functions which can be used by modules of all layers. (Eg. RTOS, Diagnostic Error Mgr etc..), partly ECU hardware and application dependent (like ECU State Manager) or hardware and μC independent

The Diagnostic Event Manager is responsible for processing and storing diagnostic events (errors) and associated FreezeFrame data.

The module Diagnostic Log and Trace supports logging and tracing of applications. It collects user defined log messages and converts them into a standardized format.

All detected development errors in the Basic Software are reported to Development Error Tracer.

The Diagnostic Communication Manager provides a common API for diagnostic services

The Debugging module supports debugging of the AUTOSAR BSW. It interfaces to ECU internal modules and to an external host system via communication

Memory Services:

The Memory Services consist of one module, the NVRAM Manager. It is responsible for the management of non volatile data (read/write from different memory drivers). It provides non volatile data to the application in a uniform way and abstracts from memory locations and properties. And also provide mechanisms for non volatile data management like saving, loading, checksum protection and verification, reliable storage etc

Communication services:

Communication service consists of below components

• COM: AUTOSAR COM is a module between the RTE and the PDU Router. It is responsible for providing Signal level access to the application layer and PDU level access to the lower layers independent of the protocol.It packs the signals to a PDU at the transmitter and unpacks the received PDU to provide signal level access to the application at the receiver. At the PDU level, COM is responsible for grouping of the PDUs, starting and stopping of the PDU groups.
• PDU Router: PDU Router is a module responsible for routing the PDU to the respective Bus Specific Interface modules.Above the PduR module all the PDUs are protocol independent, and below PduR all the PDUs are routed to the protocol specific modules. PduR is also responsible for PDU level gatewaying i.e. transmitting the received PDU from one Bus Specific Interface module to other Bus Specific Interface module.Gatewaying can also be done when a PDU is to be routed from one controller to another over the same protocol.
• CAN State Manager: This module shall implement the control flow for the respective bus. The CAN State Manager (CanSM) is a member of the Communication Service Layer.It interacts with the Communication Hardware Abstraction Layer and the System Service Layer
• CAN Network Manager: The AUTOSAR CAN Network Management is a hardware independent protocol tools that can only be used on CAN network.Its main purpose is to coordinate the transition between normal operation and bus-sleep mode of the network. The CAN Network Management (CanNm) function provides an adaptation between network Management Interface (NmIf) and CAN Interface (CanIf) module
• CAN Transport Protocol: The basic services offered by the Can TP module are segmentation of messages which have a payload of more than 8 bytes, transmission of the messages with flow control and reassembling the segmented messages at the receiver