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

1 – Wire®
Devices
Type #
Table 6.3 FILHITx Bit Definitions.
FILHIT2 FILHIT1 FILHIT0 Description
0 0 0 Perform A/D conversion on AN1.
0 0 1 Read Digital Input pins.
0 1 0 Write Value to Digital Output 1.
0 1 1 Write Value to Digital Output 2.
1 0 0 Change Node Address.
1 0 1 Turn off Digital Outputs 1 and 2.
1 1 1 Not Used
# of
CAN
Nodes
# of
Receiving
CAN
Nodes
Table 6.4 Test Results.
CAN Bus
Speed (kbps)
203
1 – Wire®
Bus Speed
(kbps)
Hot-
Swapped
(1 – Wire®)
Length of
Test
(min)
Failures
DS1996 3 2 1 10 14 Yes 60 No
DS1996 3 2 2 10 14 Yes 60 Yes 2
DS1996 3 2 1 10 140 Yes 18 Yes 1
DS1996 3 2 2 10 140 Yes 11 Yes 1
DS1996 3 2 1 125 14 Yes 60 No
DS1996 3 2 2 125 14 Yes 60 Yes 2
DS1996 3 2 1 125 140 Yes 14 Yes 1
DS1996 3 2 2 125 140 Yes 24 Yes 1
1 This failure resulted in loss of messages to the 1 – Wire® devices from the CAN bus.
2 This failure resulted in loss of messages to the 1 – Wire® devices, but did not require a hard reset.
From Table 6.4, lost CAN bus messages are noted in all cases where running the 1 –
Wire® bus in overdrive speed. As was the case with the test performed in Section 6.2.1.2,
debugging the system found that if a CAN bus message came in while running the 1 – Wire®
bus in overdrive and the 1 – Wire® devices were not all operating in overdrive speed yet, the
present CAN bus message got dropped. Although, technically this is still not a failure in the
sense of a catastrophic failure, it is still a problem in that if this had been a safety-critical system,
any loss of data or messages could be catastrophic.
When sending a 1 – Wire® command to multiple CAN nodes it was sometimes noted
that the data received from the CAN nodes was not the data requested by the 1 – Wire®
Master and stored by the 1 – Wire® slaves. For instance, consider the second test case in Table