|
Hi All, I want to add a 100Hz external reference clock to my HC12 hardware (D60A).I am planning to use SG555 or LM555 as a 100Hz square wave generator. Is there anybody using LM555 in automotive application? Is it advicable to use this chip in automotive environment? Please advice. Thanks and Regards Venu __________________________________________________ |
|
|
LM555 in Automotive application
Started by ●December 14, 2002
Reply by ●December 16, 20022002-12-16
|
Venu: Have you considered generating your 100 Hz using one of the timer output compares? That would reduce costs, and consume only 1 I/O. Regards-- 607-656-2597 -----Original Message----- From: K.P.Venu [mailto:] Sent: Saturday, December 14, 2002 12:03 AM To: Subject: [68HC12] LM555 in Automotive application Hi All, I want to add a 100Hz external reference clock to my HC12 hardware (D60A).I am planning to use SG555 or LM555 as a 100Hz square wave generator. Is there anybody using LM555 in automotive application? Is it advicable to use this chip in automotive environment? Please advice. Thanks and Regards Venu __________________________________________________ ------------------------ Yahoo! Groups Sponsor ---------------------~--> Get 128 Bit SSL Encryption! http://us.click.yahoo.com/CBxunD/vN2EAA/xGHJAA/dN_tlB/TM ---------------------------------~-> -------------------- ">http://docs.yahoo.com/info/terms/ |
|
|
Reply by ●December 16, 20022002-12-16
|
Hi Dave, Actually I want to generate an external reference clock to monitor some internal timings. The ECT module already filled with 6 capture inputs and 2 compare ouputs (for two different timings). I am also using the modulus down counter as an another timer. Venu --- Kellogg Dave <> wrote: > Venu: > Have you considered generating your 100 Hz using one > of the timer output > compares? That would reduce costs, and consume only > 1 I/O. > > Regards-- > > 607-656-2597 > Hi All, > I want to add a 100Hz external reference clock to my > HC12 hardware (D60A).I am planning to use SG555 or > LM555 as a 100Hz square wave generator. > Is there anybody using LM555 in automotive > application? > Is it advicable to use this chip in automotive > environment? > Please advice. > Thanks and Regards > Venu __________________________________________________ |
Reply by ●December 16, 20022002-12-16
|
Venu: Sounds like high utilization. Have you considered a programmable divider on e-clock, such as the 47HC7292? Divides from 2**2 to 2**31. Just a thought. Of course, it sounds as if you ready *don't* want anything derived from the MCU itself, if your intent is to cross-check the MCU. 607-656-2597 -----Original Message----- From: K.P.Venu [mailto:] Sent: Monday, December 16, 2002 9:43 AM To: Subject: RE: [68HC12] LM555 in Automotive application Hi Dave, Actually I want to generate an external reference clock to monitor some internal timings. The ECT module already filled with 6 capture inputs and 2 compare ouputs (for two different timings). I am also using the modulus down counter as an another timer. Venu --- Kellogg Dave <> wrote: > Venu: > Have you considered generating your 100 Hz using one > of the timer output > compares? That would reduce costs, and consume only > 1 I/O. > > Regards-- > > 607-656-2597 > Hi All, > I want to add a 100Hz external reference clock to my > HC12 hardware (D60A).I am planning to use SG555 or > LM555 as a 100Hz square wave generator. > Is there anybody using LM555 in automotive > application? > Is it advicable to use this chip in automotive > environment? > Please advice. > Thanks and Regards > Venu __________________________________________________ ------------------------ Yahoo! Groups Sponsor ---------------------~--> Get 128 Bit SSL Encryption! http://us.click.yahoo.com/CBxunD/vN2EAA/xGHJAA/dN_tlB/TM ---------------------------------~-> -------------------- ">http://docs.yahoo.com/info/terms/ |
|
|
Reply by ●December 16, 20022002-12-16
|
Yes. It is for a cross-check of MCU timings. --- Kellogg Dave <> wrote: > Venu: > Sounds like high utilization. > > Have you considered a programmable divider on > e-clock, such as the 47HC7292? > Divides from 2**2 to 2**31. Just a thought. Of > course, it sounds as if you > ready *don't* want anything derived from the MCU > itself, if your intent is > to cross-check the MCU. > 607-656-2597 > -----Original Message----- > From: K.P.Venu [mailto:] > Sent: Monday, December 16, 2002 9:43 AM > To: > Subject: RE: [68HC12] LM555 in Automotive > application > Hi Dave, > Actually I want to generate an external reference > clock to monitor some internal timings. > > The ECT module already filled with 6 capture inputs > and 2 compare ouputs (for two different timings). > I am also using the modulus down counter as an > another > timer. > Venu __________________________________________________ |
Reply by ●December 16, 20022002-12-16
|
Venu I dont like the idea of using the 555 as a freq reference in Automotive, as the frequency based on the capacitor value, and the temperature conditions are not good for such an application. Try connect 32khz crystal to 4060 chip, and use one of its prescale outputs Benny ---------- Forward Message ---------- To: From: "K.P.Venu" <> Date: Mon, 16 Dec 2002 06:42:39 -0800 (PST) Subject: RE: [68HC12] LM555 in Automotive application Hi Dave, Actually I want to generate an external reference clock to monitor some internal timings. The ECT module already filled with 6 capture inputs and 2 compare ouputs (for two different timings). I am also using the modulus down counter as an another timer. Venu --- Kellogg Dave <> wrote: > Venu: > Have you considered generating your 100 Hz using one > of the timer output > compares? That would reduce costs, and consume only > 1 I/O. > > Regards-- > > 607-656-2597 > Hi All, > I want to add a 100Hz external reference clock to my > HC12 hardware (D60A).I am planning to use SG555 or > LM555 as a 100Hz square wave generator. > Is there anybody using LM555 in automotive > application? > Is it advicable to use this chip in automotive > environment? > Please advice. > Thanks and Regards > Venu __________________________________________________ -------------------- ">http://docs.yahoo.com/info/terms/ ---------- End of Forward Message ---------- |
|
|
Reply by ●December 16, 20022002-12-16
|
Thanks Benny, I have the same doubts. I will try your method. Venu --- In , RTS development - Benny Rabin <benny@r...> wrote: > Venu > > I dont like the idea of using the 555 as a freq reference in Automotive, as the > frequency based on the capacitor > value, and the temperature conditions are not good for such an application. > Try connect 32khz crystal to 4060 chip, and use one of its prescale outputs > > Benny |
Reply by ●December 17, 20022002-12-17
|
You can build a very simple oscillator with pretty good stability using a Schmidt input inverter ('HC14) and one resistor and one capacitor as long as you have a fairly stable supply and decent components. Another approach would be to use the 'HC4538 Monostable Multivibrator. These are highly stable devices when used with decent componts. Bob Smith --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-1065 ----- Original Message ----- From: <> To: <> Sent: Monday, December 16, 2002 10:07 PM Subject: [68HC12] Re: LM555 in Automotive application > Thanks Benny, I have the same doubts. > I will try your method. > Venu > --- In , RTS development - Benny Rabin > <benny@r...> wrote: > > Venu > > > > I dont like the idea of using the 555 as a freq reference in > Automotive, as the > > frequency based on the capacitor > > value, and the temperature conditions are not good for such an > application. > > Try connect 32khz crystal to 4060 chip, and use one of its prescale > outputs > > > > Benny > > > -------------------- > > ">http://docs.yahoo.com/info/terms/ > |
Reply by ●December 17, 20022002-12-17
|
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 Silicon Engines 2101 Oxford Road Des Plaines, IL 60018 USA 847-803-6860 Fax 847-803-6870 ----- Original Message ----- From: kp_venu <> To: Sent: Monday, December 16, 2002 9:07 PM Subject: [68HC12] Re: LM555 in Automotive application Thanks Benny, I have the same doubts. I will try your method. Venu --- In , RTS development - Benny Rabin <benny@r...> wrote: > Venu > > I dont like the idea of using the 555 as a freq reference in Automotive, as the > frequency based on the capacitor > value, and the temperature conditions are not good for such an application. > Try connect 32khz crystal to 4060 chip, and use one of its prescale outputs > > Benny -------------------- |
|
|
Reply by ●December 18, 20022002-12-18
|
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 |
