DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...
DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ... DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...
In addition to being conducted at two different speeds, the tests are also conducted using both 11-bit and 29-bit message identifier fields. Without hot swapping, no failures are noted while running any of the tests but a considerable degradation in the performance is noticed in the bandwidth when using the extended 29-bit message identifiers at the 125 kbps speeds. When making an attempt to perform hot swapping on any individual node (regardless of any of the eight tests being conducted or bus speeds), it is noticed that all communications on the CAN bus come to a halt and the only way to restore communications is to perform a hard reset, powering down the Altera DE2 board and all CAN nodes. It is clear that more extensive testing is needed to find a solution for this problem. It is common that adding additional components to a network most often requires shutting down the entire network to prevent costly system errors, as was evident in this case. The ability to plug-in or remove a CAN node from the system would be a valued asset for many CAN applications. At this time, it is believed that the transceivers on each CAN node are the root cause of the failure, since hot swapping CAN nodes requires that the transceiver output remain stable during the unpowered to power-up transition without disturbing ongoing CAN network communications. Since many CAN transceivers on the market today have very low output impedance when unpowered, this causes the device to sink any signal present on the bus and would effectively shut down all bus communication. Clearly, further research and testing is needed in this area along with CAN transceivers from different manufacturers being replaced on individual CAN nodes. 189
5.3.21.4 Send Basic Frame Test (send_frame_basic) For this test, messages are placed on the CAN bus for reception by all nodes using only the 11-bit message identifier (CAN 2.0A). The Altera DE2 Development and Education board is connected with 30 CAN nodes on the network. The test setup is the same as that shown previously in Figure 5.40. Again only two data rates are tested, 10 kbps and 125 kbps, since these two data rates are closest to those data rates supported by most 1 – Wire® devices. Table 5.21 shows the results for this test. Table 5.21 Send Basic Frame (send_frame_basic) Test Results. Data Rate Messages Sent Data Bytes Length of test Hot Swapped Failures 10 kbps 225,419 8 60 min No None 10 kbps 253 8 60 min Yes Yes 125 kbps 2,748,624 8 60 min No None 125 kbps 119 8 60 min Yes Yes Again, while attempting to hot swap CAN nodes on the network, communication on the bus is halted and the only way to restore communications is to perform a hard reset, powering down the Altera DE2 board and all CAN nodes. This is clearly an issue that merits further research and exploration to fully understand the nature and root cause of the failure when attempting to hot swap nodes on the CAN bus. 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. When hot swapping of nodes is not attempted, no failures are noted. For the data rate of 10 kbps and 30 CAN nodes, no significant degradation in bandwidth or reduction in total messages transferred is realized. However, while conducting this test at 125 kbps with 30 CAN nodes, a slight degradation in bandwidth is noticed as can be seen by the lower amount of messages transferred within the same amount of time from the test conducted here versus the test conducted in Section 5.3.21.2 (compared to data in Table 5.20 190
- Page 163 and 164: 5.2.8.4 Command Recognition (cmd_re
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- Page 167 and 168: compensate for the propagation dela
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- Page 183 and 184: TSEG22 - TSEG10: Time Segment Bits.
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5.3.21.4 Send Basic Frame Test (send_frame_basic)<br />
For this test, messages are placed on the CAN bus for reception by all nodes using only<br />
the 11-bit message identifier (CAN 2.0A). The Altera DE2 Development and Education board<br />
is connected with 30 CAN nodes on the network. The test setup is the same as that shown<br />
previously in Figure 5.40. Again only two data rates are tested, 10 kbps and 125 kbps, since<br />
these two data rates are closest to those data rates supported by most 1 – Wire® devices. Table<br />
5.21 shows the results for this test.<br />
Table 5.21 Send Basic Frame (send_frame_basic) Test Results.<br />
Data Rate Messages Sent Data Bytes Length of test Hot Swapped Failures<br />
10 kbps 225,419 8 60 min No None<br />
10 kbps 253 8 60 min Yes Yes<br />
125 kbps 2,748,624 8 60 min No None<br />
125 kbps 119 8 60 min Yes Yes<br />
Again, while attempting to hot swap CAN nodes on the network, communication on<br />
the bus is halted and the only way to restore communications is to perform a hard reset, powering<br />
down the Altera DE2 board and all CAN nodes. This is clearly an issue that merits further<br />
research and exploration to fully understand the nature and root cause of the failure when<br />
attempting to hot swap nodes on the CAN bus. For both data rates, the total messages sent is<br />
representative of the total number of messages sent up to the point that hot swapping of a node is<br />
attempted. When hot swapping of nodes is not attempted, no failures are noted.<br />
For the data rate of 10 kbps and 30 CAN nodes, no significant degradation in<br />
bandwidth or reduction in total messages transferred is realized. However, while conducting this<br />
test at 125 kbps with 30 CAN nodes, a slight degradation in bandwidth is noticed as can be<br />
seen by the lower amount of messages transferred within the same amount of time from the test<br />
conducted here versus the test conducted in Section 5.3.21.2 (compared to data in Table 5.20<br />
190
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