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

to be used in any type of safety-critical application environment. A simple and obvious fix to
this problem is to run similar speeds on both buses without allowing hot-swapping: either the
CAN bus at 10 kbps and the 1 – Wire® bus at 14 kbps or the CAN bus at 125 kbps and the
1 – Wire® bus at 140 kbps. The downside to this option is the reduced flexibility placed on the
combined system which is stated as being one of the big advantages of using 1 – Wire® devices
and technology.
The other type of failure from the tests conducted on the combined prototype system
occurred when sending a 1 – Wire® command to multiple CAN nodes. It was originally
thought that the cause of data loss was from receiving the response data bytes from the CAN
nodes before the 1 – Wire® Master had time to process and write the received data bytes to the
appropriate memory locations on the DS1996 1 – Wire® devices. Another possible scenario for
the source of the data loss was that data was coming in to the 1 – Wire® Master before all of the
1 – Wire® slave devices were operating in overdrive speed. After inserting numerous traps and
inserting lines of debug code, it was determined that when requesting data from multiple CAN
nodes the first byte of received data could be overwritten by the second byte of data if the 1 –
Wire® Master had not been able to successfully process the incoming data byte. However, no
definitive conclusions were reached as to the root cause of data loss. Data loss could have been a
combination of one or both scenarios. Clearly further research and testing is needed to find a
solution to prevent data loss and the idea of inserting a delay timer for the cases when 1 – Wire®
slaves are being operated at overdrive speed certainly merits exploration. No further testing was
performed with additional nodes, since it can be assumed that if failures were seen when
requesting data from two CAN nodes that this problem would only become more apparent as
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