Testing - CAN System Engineering - page 315

Fig. 6.10 ISO CAN Conformance Test coverage

The ISO conformance test is covering the lower part of the DLL and the up-
per part of the physical layer. The access points for the tests are given by the TX/
RX lines from the physical layer side. For the DLL side, the access points for the
tests are given by a unified virtual receive and transmit register interface. This sim-
plification was necessary, because real CAN chip solutions differ very much in
the register architecture, representing the processor interface. As no such standard
interface is available, a virtual standard register interface was artificially defined.
When performing these tests on the tester, the virtual registers must be mapped by
accordingly tuned test software onto the actual real register interface.
As mentioned above, the ISO standard conformance test only covers the so-
called CAN cell or core. The standard tests neither cover the individual processor
interface nor the line driver part. However, there are extended conformance test
solutions as described in the next sections.

6.3.3.2 The Processor Interface Test Types

Standard Conformance tests are performed on the assumption of a standardized
simplified received and transmitted register interface between the CAN device un-
der test and the UT. This simplification never corresponds to a real CAN imple-
mentation. However, obviously the real CAN register implementation with their
corresponding control bits have a great influence on the proper function of a CAN
device. As a result a set of additional “de facto” standard register TCs was devel-
oped. Each of these extended register TCs is dedicated to perform specific checks
on special characteristics of CAN registers.