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

5.2.8.4 Command Recognition (cmd_recognition) Test
This test checks all of the basic commands shared by almost every family of 1 – Wire®
devices available on the commercial market today. These commands include: READ_ROM
(0x33), SKIP_ROM (0xCC), MATCH_ROM (0x55), SEARCH_ROM (0xF0), WRITE_SP
(0x0F), READ_SP (0xAA), OD_SKIP_ROM (0x3C), OD_MATCH_ROM (0x69), COPY_SP
(0x55), and READ_MEM (0xF0). The command recognition test also checks 1 – Wire® reset,
overdrive reset, strong pullup enable, active high and low interrupts and some of the divisor
clock frequencies from 4 MHz up to 112 MHz (see Table 5.2).
Due to the amount of time required to run a complete test with all commands and full
range of clock frequencies, there is only a single 1 – Wire® slave device on the network. Only 1
– Wire® devices capable of supporting overdrive speeds and having an internal scratchpad area
in memory were used to conduct this test (See Table 5.7). The setup configuration, shown in
Figure 5.12, uses any configurable I/O pin on the Altera DE2 Development and Education board
to serve as the 1 – Wire® Master. Unlike the other tests run in sections 5.2.8.1 – 5.2.8.3, hot
swapping of 1 – Wire® slave devices was not performed while running this test. The main goals
of this test were to check the functionality and reliability of the different 1 – Wire® commands,
as listed above, and the commands required to have a reliable 1 – Wire® Master capable of
driving long 1 – Wire® networks. The test results, summarized in Table 5.7, verified correct
operation.
Table 5.7 Command Recognition (cmd_recognition) Test Results.
1 – Wire® Device Type 1 – Wire Probe Cables Length of test Hot Swapped Failures
DS1963L[91]
~120 min No No
DS1921G[92] ~120 min No No
DS1996[83]
DS1995[90]
DS1402-RP8+[80]
~120 min
~120 min
No
No
No
No
DS1977[93] ~120 min No No
DS1922L[94] ~120 min No No
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