CANdesc

Functions

All vehicle manufacturer specific diagnostic features are implemented and encapsulated in CANdesc. This gives the ECU application a clear signal interface. Reutilization of the ECU application is thereby supported.

CANdesc covers

• support of the total manufacturer-specific diagnostic protocol with all functional and timing constraints
• full implementation of communication related diagnostic services (e.g. $28 CommunicationControl)
• implementation of “data unit” handling ($2A, $2C) according to the OEM specification
• filtering of diagnostic requests according to service, session, service instance, format, session of service instance and security
• correct responses to diagnostic requests
• state management (depending on the CANdela database e.g. session and security handling)
• generation of a diagnostic data buffer and preservation of data consistency between application and diagnostic request (functional, physical and multiple simultaneous)
• a DAP (Diagnostic Adaptation Protocol) module for diagnostics of MOST ECUs (on request)

Code size

Of course, the size of the automatically generated code in terms of RAM and ROM is greater than that of manually optimized modules. However, if one considers the "dead paths" (approx. 10%-20%) and often suboptimal extensions that occur over the duration of a project with manually written code, the size of the automatically generated code is generally no greater than that of manually encoded modules.

Example of code size

Microprocessor: Motorola HC12, MC9S12DP256;
Cosmic compiler 4.5 with an implementation of 10 diagnostic services and 30 subfunctions with data packets:
Code size: approx. 5.5 kByte
Tables and constants: approx. 700 bytes
RAM: approx. 70 bytes plus bytes for the diagnostic buffer.
For average sized applications with approx. 120 sub functions the code size increases to approx. 9kByte.

Supplemental Services

Vector offers the following types of project services:

• Adaptation of the application to CANdesc
• Implementation of fault memory concepts
• Process consultation services in the diagnostic area
• Testing of ECU diagnostic implementation