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

a problem in that important CAN messages can be lost with no indication of a lost message or
need for retransmission.
As discussed in Section 4.3.4, there are two ways to get an overdrive-capable slave
device into overdrive mode: Overdrive Skip command, and Overdrive Match command. Also,
despite the extra command and reset cycle necessary to get 1 – Wire® devices into overdrive
mode, using overdrive obtains the device identification number in less than half the time required
at standard speed.
One possible solution to this problem is to implement either a FIFO or prioritized FIFO
buffer to possibly prevent CAN bus messages from being discarded and retain them until all 1
– Wire® devices are operating at overdrive speed. Another possible solution is to implement
some type of handshaking or acknowledgement when CAN bus messages are transmitted for 1
– Wire® devices.
6.2.1.3 Test Results – 1 – Wire® Master requests data from CAN Nodes
Again for this test, three DS1996 1 – Wire® devices and two CAN nodes are present
on the network. The 1 – Wire® devices and CAN bus nodes are connected as shown in Figure
6.2. The CAN node addresses remain set at 1 and 2 respectively. Unlike the test conducted in
Section 6.2.1.2, the CAN nodes utilized for this test have been modified to prevent the
automatic transmission of the A/D conversion result every 500 ms. Also, the 1 – Wire® Master
was modified to have the capability to send a command to any one particular node or all of the
CAN nodes. Additional Verilog® code in the form of a For loop was added to simulate a
broadcast command being sent from the 1 – Wire® Master. Whether this command is executed
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