| ??? 01/26/03 10:13 Read: times |
#37288 - RE: Code Recovery with Watch Dog Timers |
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and especially Sample #4: How to use software traps?. i don't recall anyone saying to use software traps INSTEAD of watchdogs. but if all you have is an EXTERNAL watchdog circuit, then all you will get is a reset, with no knowledge of the cause. even if the trips are occurring on your workbench, you could probably debug it quicker if you recognize the possibilities in advance, and have internal diagnostic firmware designed to help recognize those possibilities. for instance, if the traps are filled with subroutine calls to a diagnostic routine (instead of just spin loops), the diagnostic routine could save the system state, including the stacked return address for the subroutine call made by the trap. if the stack indicates the same return address every time, a software fault is indicated. if it indicates a different return address every time, a hardware fault is indicated (but not guaranteed). one time, to help debug a lockup problem, i filled spare PROM with spin loops (LJMP $). the h/w engineer hooked up the bus to a logic analyzer, and we watched the address bus traffic. bam! the cpu hit one of the loops. AS WE WATCHED, it then jumped to another loop. at that point we stopped considering the firmware as a possible cause, and the problem was traced to faulty connections between the daughterboard and motherboard on that unit. meanwhile, let's see what Ganssle says in next month's column ... it looks interesting ... <table><tr><td>james</td><td> </td><td> www.jameshinnant.com</td></tr></table> </html> |
| Topic | Author | Date |
| Code Recovery with Watch Dog Timers | 01/01/70 00:00 | |
RE: expanded on above | 01/01/70 00:00 | |
| RE: Code Recovery with Watch Dog Timers | 01/01/70 00:00 | |
| RE: Code Recovery with Watch Dog Timers | 01/01/70 00:00 | |
| RE: Code Recovery with Watch Dog Timers | 01/01/70 00:00 | |
| RE: Code Recovery with Watch Dog Timers | 01/01/70 00:00 | |
| RE: Code Recovery with Watch Dog Timers | 01/01/70 00:00 |