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

6.4. There are two receiving CAN nodes and both the CAN bus and 1 – Wire® bus are
operating at their slower speeds of 10 kbps and 14 kbps, respectively. Only in certain instances
is data lost when it is requested from the CAN nodes. After inserting lines of debug code and
recording the commands sent to the CAN nodes from the 1 – Wire® Master, no correlation is
found between one particular command being sent to the CAN nodes from Table 6.4 and data
loss. It was discovered, however, that in certain cases if both CAN nodes send their data
before it can be fully processed by the 1 – Wire® Bus Master, data loss to the 1 – Wire® slaves
occurs. This results in the first byte of requested data being overwritten by the second byte of
data. The CAN node that transmits its byte of data first determines which byte of data is
actually stored to the 1 – Wire® slaves. It is also discovered that there is no loss of data in the
commands being send from the 1 – Wire® Master to the receiving CAN nodes.
Again, a possible solution to this problem is to implement either a FIFO or a prioritized
FIFO buffer to possibly prevent the data requested from the CAN nodes from being
overwritten. As was mentioned in Section 6.2.1.2, another possible solution is to implement
some type of handshaking or acknowledgement when the data byte requested from the CAN
nodes are actually successfully stored in the memory of the DS1996 1 – Wire® devices. Even
though this would impact the speed of the bus, the reliability gained by preventing data loss
would greatly outweigh the reduction in data throughput.
Finally, no conclusion is reached regarding the loss of data in the test cases (tests 3,4,7,
and 8) where the 1 – Wire® slaves are operating at overdrive speed. It is unknown as to whether
the data loss to the 1 – Wire® slaves is a result of all devices not operating in overdrive speed or
if data loss is a result of both CAN nodes transmitting the requested data before the 1 – Wire®
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