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Venu, Yes, you might have a crystal problem. Just to know for sure if this is the problem, you can connect 32khz oscillator instead of the crystal and check if it solved the problem Benny ---------- Forward Message ---------- Thanks Bob Smith and Kerry. Kerry, Recently I had a "slow clock" problem in my system. When I discussed this with Motorola engineer, he said it may due to crystal startup problem and suggested to check the LIMP-HOME flag before writing to PLL registers. I have successfully implemented this (thanks to Darci) and till date no problem has been reported from the field. But still I am not able to conclude that it is a crystal problem because I am using an External Watchdog timer which has a Power-ON reset delay of 600ms and timeout period of 150ms. I believe this power-on delay is more than enough to start the oscillation. I am using a voltage monitor too.(MC33164) I have added two more things to check the slow clock, 1. External watchdog refreshment time modified to 100ms so that any slow clock will delay the refresh time and initiate a reset. 2. Monitor Timer0 and MDC occurrence using RTI interrupt for a predefined time (say 65.535ms). Above methods are good for detecting slow clock but not smart enough to detect a faster clock (due to wrong settings of PLL registers). So I am planning to input a low frequency external reference signal for counting the clock. This may not be a good idea but I need to do some quick fix for this problem. If anybody has any better idea please tell me. Thanks and Best Regards, Venu --- In , "Kerry Berland" <kerry@s...> wrote: > Since the 68HC12 has its own internal timebase, > not sure the purpose of an external timer....?? > > Unless maybe you're thinking of a kind of external > watchdog timer? So that in the event of a hardware > or software failure of the main MCU, the overall system > would recover? If so, there are various reset generator > chips that include external watchdog timers. Also there > are power supply chips that include both a low voltage > reset, and a watchdog timer. > > Best regards, > > Kerry Berland > kerry@s... > Silicon Engines > 2101 Oxford Road > Des Plaines, IL 60018 USA > 847-803-6860 > Fax 847-803-6870 -------------------- ">http://docs.yahoo.com/info/terms/ ---------- End of Forward Message ---------- |
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LM555 in Automotive application
Started by ●December 14, 2002
Reply by ●December 18, 20022002-12-18
Reply by ●December 18, 20022002-12-18
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Hi, You can use one of the PWM outputs to this job. Thanks and Best Regards ___________________________________________ Baskaran Kasimani Senior Engineer, Systems Delphi Automotive Systems Singapore Pte Ltd Delco Electronics Systems Singapore Design Centre - Powertrain 501, Ang Mo Kio Industrial Park 1 Singapore 569621 Tel : (65) 6450 8652 Fax : (65) 6552 4459 email: |
Reply by ●December 18, 20022002-12-18
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Benny, Actually we planned to use 16Mhz oscillator for our h/w. For some cost saving purpose we moved to 4Mhz crystal + PLL. Venu --- In , RTS development - Benny Rabin <benny@r...> wrote: > Venu, > > Yes, you might have a crystal problem. > > Just to know for sure if this is the problem, you can connect 32khz oscillator > instead of the crystal and check if it solved the problem > > Benny > > ---------- Forward Message ---------- > Thanks Bob Smith and Kerry. > Kerry, > Recently I had a "slow clock" problem in my system. > When I discussed this with Motorola engineer, he said it may due to > crystal startup problem and suggested to check the LIMP-HOME flag > before writing to PLL registers. I have successfully implemented this > (thanks to Darci) and till date no problem has been reported from the > field. > > But still I am not able to conclude that it is a crystal problem > because I am using an External Watchdog timer which has a Power-ON > reset delay of 600ms and timeout period of 150ms. I believe this > power-on delay is more than enough to start the oscillation. > I am using a voltage monitor too.(MC33164) > > I have added two more things to check the slow clock, > 1. External watchdog refreshment time modified to 100ms so that any > slow clock will delay the refresh time and initiate a reset. > 2. Monitor Timer0 and MDC occurrence using RTI interrupt for a > predefined time (say 65.535ms). > Above methods are good for detecting slow clock but not smart enough > to detect a faster clock (due to wrong settings of PLL registers). So > I am planning to input a low frequency external reference signal for > counting the clock. This may not be a good idea but I need to do some > quick fix for this problem. > > If anybody has any better idea please tell me. > > Thanks and Best Regards, > Venu > --- In , "Kerry Berland" <kerry@s...> wrote: > > Since the 68HC12 has its own internal timebase, > > not sure the purpose of an external timer....?? > > > > Unless maybe you're thinking of a kind of external > > watchdog timer? So that in the event of a hardware > > or software failure of the main MCU, the overall system > > would recover? If so, there are various reset generator > > chips that include external watchdog timers. Also there > > are power supply chips that include both a low voltage > > reset, and a watchdog timer. > > > > Best regards, > > > > Kerry Berland > > kerry@s... > > Silicon Engines > > 2101 Oxford Road > > Des Plaines, IL 60018 USA > > 847-803-6860 > > Fax 847-803-6870 > |
