DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

For the synthesizable CAN Controller, there was an additional test considered but
never fully implemented: self_reception_request test. In this test, there are two different modes
of operation. First, the CAN module performs an internal loop back (default), which can be
used for self-test operation. In this mode, a dummy Acknowledge bit is provided, thereby
eliminating the need for another node on the bus to provide the Acknowledge bit (i.e. the module
treats its own transmitted message as a message received from a remote node). The rx input pin
is ignored and the tx output pin goes to the recessive state (logic ‘1’). Both transmit and receive
interrupts are generated. Alternatively, if the user desires, the current message can be queued for
transmission without disabling the receiver. It will receive the message only if the Acceptance
Filter recognizes the message ID. This test was originally considered as a part of a plan to also
implement a FIFO or prioritized FIFO buffer in the synthesizable CAN Controller. But after
much time and consideration it was thought that a better approach would be to implement a FIFO
or prioritized FIFO buffer as a separate entity in the design and not integrate it as part of the
CAN Controller. So for this reason development and implementation of this test was dropped.
From the test results of those performed in Chapter 6, the combined 1 – Wire® to CAN
prototype system clearly needs more debugging and testing before becoming a fully-functional
production prototype. This is evident from the failures noted in Tables 6.2 and 6.4 as a result of
the two tests performed. Even though neither of the two tests performed had a failure from a
catastrophic point of view, both tests had failures concerning lost CAN bus messages when
trying to run 1 – Wire® devices in overdrive speed and also when trying to hot-swap 1 – Wire®
devices. As stated previously, this is primarily attributed to the extra steps required to get all 1 –
Wire® devices into overdrive mode. This is still a big problem especially if the system is going
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