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microlab
Joined: 04 Mar 2006
Posts: 106
Helped: 3
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 27 Feb 2008 14:36 89c2051 |
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dear friends
what will happen if we do not connect the capacitor from reset pin to +Vcc?
is there any documents related to power down mode of 8051 is available?
i would like to know more about the cold boot and warm boot
and other aspects about the power down mode
thanking you
ml
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rajeshkumar123
Joined: 27 Dec 2007
Posts: 179
Helped: 19
Location: Chennai-India
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27 Feb 2008 14:45 89c2051 reset capacitor |
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hi,
The capcitor maintains the logic high at the reset pin to avoid false reset when power supply dips for a few micro secs.
Its is recommended that the RC time constant be equal to atleast 100 machine cycles to guarantee a quality reset.
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Khurram Shahzad
Joined: 14 Oct 2006
Posts: 16
Helped: 1
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29 Feb 2008 7:04 89c2051 power down |
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Wrong!
The capacitor actually give reset pulse at power ON.
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29 Feb 2008 7:04 Ads |
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microlab
Joined: 04 Mar 2006
Posts: 106
Helped: 3
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29 Feb 2008 12:33 reset cho 89s2051 |
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dear friends
thank you for the reply
in at 89c2051 the capacitor is connected to +vcc
any body can get me more about the idle and powerdown modes of at 89c2051?
and about cold reset and warm reset?
regards
ml
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rajeshkumar123
Joined: 27 Dec 2007
Posts: 179
Helped: 19
Location: Chennai-India
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29 Feb 2008 15:27 89c2051 powerdown |
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Hi,
i have mentioned that RC constant to be equal to 100 Machine cycles which for the reset pulse.
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drbizzarow
Joined: 24 May 2006
Posts: 276
Helped: 9
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29 Feb 2008 23:05 89c2051 |
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not sure !!! but little bit i know 2051 have pwr dwn and cold boot and warm boot
you can verify by downloading datasheet form atmel website.
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laktronics
Joined: 06 Jan 2007
Posts: 945
Helped: 156
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01 Mar 2008 8:54 Re: 89c2051 |
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Hi,
Please read this EDN article for details, but you can avoid all these problems if you can use the latest 89S2051,which recovers from power down mode with external interrupts, in which case, the controller working environments are not changed and it truly lands up after a long sleep as if nothing has happened.
Regards,
Laktronics
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mkiani
Joined: 11 Apr 2007
Posts: 107
Helped: 1
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04 Mar 2008 14:26 89c2051 |
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| capacitor and resistor in reset pin perform power up reset.by starting theciruit capacitor is decharge (vc=0)so vcc drop on reset.then capasitor charge and after 5t(t=r*c)vc reach to vcc so voltage drop on reset pin=0 so with starting the circuit uc reset and then go in normal mod.
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