UDS Protocol Stack Architecture | UDS architecture

This page covers architecture of UDS protocol stack layers. It mentions functions of layers of UDS Protocol architecture.

UDS stack architecture

UDS stands for Unified Diagnostic Services. This protocol has been developed to provide tester capabilities to communicate with ECUs (Electronic Control Units) of various vehicles for diagnostics purpose. It follows client server architecture. Tester tool functions as client which sends service requests to the ECU. ECU functions as server and responds tester tool as per service request message received.

UDS Protocol Stack Architecture for CAN bus

UDS supports various interface standards such as FlexRay, IP, K-Line, LIN, CAN, KWP 2000 etc. Figure depicts UDS Protocol Stack Architecture for CAN bus and its comparison with OSI stack. The physical layer and data link layer specifications of CAN interface are defined in ISO 11898. UDS specifications are defined in ISO 14229 for session layer and application layer.

Following are the functions and features of UDS stack with CAN interface.
➨Application layer : This layer deals with various functional requirements viz. communication between client and server, UDS services, positive & negative response codes and other parameters such as DTCs, DIDs etc. It is mentioned in ISO 14229-1.
➨Presentation layer : This layer is specific to implementation by different vehicle manufacturers.
➨Session layer : The various services to session layer are defined in ISO 14229-2. It defines primitives for service request, indication, confirmation etc.
➨Transport and network layer : These layers define communication mechanism for diagnostic requests and their responses. It is defined in ISO 15765-2. It mentions CAN frame structure which enables multi-frame payload communication.
➨Data link layer : For CAN bus, it is specified in ISO 11898-1.
➨Physical layer : For CAN bus, it is specified in ISO 11898-2.
➨Refer article on OSI stack layers and their functions.

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