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

which is in section 5.3.21.2). While this is only a 2.45% reduction in total messages transferred
in going from one node to thirty nodes, this issue could become critical as more nodes are added
to the system.
5.3.21.5 Send Extended Frame Test (send_frame_extended)
In conducting this test, messages are placed on the CAN bus using the extended 29-bit
message identifier field. The Altera DE2 board is connected with 30 CAN nodes on the
network. The test setup is the same as that shown previously in Figure 5.40. Only two data rates
are used in conducting this test: 10 kbps and 125 kbps. Again, these values were selected
because they most closely match those speeds supported by 1 – Wire® devices. The results for
this test are shown in Table 5.22.
Table 5.22 Send Extended Frame (send_frame_extended) Test Results.
Data Rate Messages Sent Data Bytes Length of test Hot Swapped Failures
10 kbps 208,615 8 60 min No None
10 kbps 1,548 8 60 min Yes Yes
125 kbps 2,531,027 8 60 min No None
125 kbps 5,483 8 60 min Yes Yes
For this test, no failures are noted when hot swapping nodes is not attempted. But when
attempting to hot swap nodes, communication on the bus is again halted and the only way to
restore communications is to perform a hard reset, powering down the Altera DE2 board and all
CAN nodes. For both data rates, the total messages sent is representative of the total number
of messages sent up to the point that hot swapping of a node is attempted. As stated previously,
this is an issue that merits further investigation and research.
While conducting this test with 30 CAN nodes, degradation in bandwidth is realized
even at the slower speed of 10 kbps. While only a 7.98% reduction in total messages transferred,
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