[picsig] Help needed with MCLR reset

[J.P. Rouland]

Andrew,
Read the PIC specs on reset: I kind of remember seeing some "nasty" 
details, like timing, or speed of signal change on the reset pin.
Don't remember now, but I remember thinking it was not as 
straightforward as most other micros.
PIC data sheets can be found on the web. Got them through Google search.
Wish I had time to go back search for you, but I'm in a hurry....
J.P. NQ6T

Andrew Rich wrote:

> Lee,
> 
> My name is Andrew.
> 
> The LCD is fine and happy to a power up. You can sit there all day and 
> turn the whole cct on and off.
> 
> But when you just reset the PIC it does not always come back the same as 
> a power cycle.
> 
> 
> 
> ----------------------------------------------------------------------
> Andrew Rich (VK4TEC)
> 
> 
> 
> 
> 
>> From: "Lee De Vries" <LDEVRIES at gordontafe.edu.au>
>> Reply-To: TAPR PIC Mailing List <picsig at lists.tapr.org>
>> To: "TAPR PIC Mailing List" <picsig at lists.tapr.org>
>> Subject: RE: [picsig] Help needed with MCLR reset
>> Date: Thu, 22 Jul 2004 13:23:08 +1000
>>
>>
>> Hi Rich,
>>
>> Have to go to class now, but I think I understand your problem.  LCD's 
>> are tricky to reset & there was a error in the initial Hitachi data 
>> sheet.  They are temperature sensitive & if you don't get it right, 
>> then it will behave as if the CPU is not resetting.  Been there done 
>> that. Get back to you.
>>
>>
>> Lee
>>
>>
>> -----Original Message-----
>> From: Andrew Rich [mailto:vk4tec at hotmail.com]
>> Sent: Thursday, 22 July 2004 11:28 AM
>> To: picsig at lists.tapr.org
>> Subject: RE: [picsig] Help needed with MCLR reset
>>
>>
>> Thanks Lee,
>>
>> I am using an LCD.
>>
>> I have to hold the MCLR down for one to two seconds to get the thing to
>> clean reset, but does not all the time work.
>>
>> Sometimes the LCD goes nuts. and the system does not restore properley .
>>
>> I found out about the RAM staying put yesteday, and I am looking into if
>> this is casuing me hassles.
>>
>> Thanks !
>>
>>
>>
>> ----------------------------------------------------------------------
>> Andrew Rich (VK4TEC)
>>
>>
>>
>>
>>
>> >From: "Lee De Vries" <LDEVRIES at gordontafe.edu.au>
>> >Reply-To: TAPR PIC Mailing List <picsig at lists.tapr.org>
>> >To: "TAPR PIC Mailing List" <picsig at lists.tapr.org>
>> >Subject: RE: [picsig] Help needed with MCLR reset
>> >Date: Thu, 22 Jul 2004 09:55:47 +1000
>> >
>> >
>> >Hi,
>> >
>> >I am not sure what you mean by a "clean reset" as opposed to perhaps a
>> >"non-clean reset".
>> >
>> >If you mean that all file registers are reset to 0x00, I think a 
>> power down
>> >is required ( for perhaps a few seconds) will be required.
>> >
>> >Resetting it with MCLR, will obviouslt reset PC and probably most 
>> FSR's but
>> >not RAM.
>> >
>> >I have never had a problem with resets and have now used 100's of 
>> PICs in
>> >about 40 designs that I have done.
>> >
>> >Perhaps a 10uF Tantalum to ground will ensure that /MCLR stays low for
>> >sufficient time to reset properly.
>> >
>> >Lee VK3PK
>> >
>> >
>> >
>> >-----Original Message-----
>> >From: David VanHorn [mailto:dvanhorn at cedar.net]
>> >Sent: Wednesday, 21 July 2004 11:05 PM
>> >To: TAPR PIC Mailing List; Andrew, VK4BAB; vk4khp; TAPR PIC Development
>> >Special Interest Group
>> >Subject: Re: [picsig] Help needed with MCLR reset
>> >
>> >
>> >At 05:48 PM 7/19/2004 +1000, Andrew Rich wrote:
>> >
>> > >Howdy,
>> > >
>> > >Having problems getting the PIC to clean reset.
>> > >
>> > >I have MCLR enabled and held high with a 10k resistor. I sink it to 
>> gnd
>> > >using a button.
>> > >
>> > >Ideas ? Seems to lock up and not reset well
>> >
>> >1: not much pullup, 4.7k would be safer, or even 1k.
>> >2: contact bounce. Add a 0.1uF cap across the switch, located at the 
>> micro.
>> >3: EMI/ESD pickup on the wire, add 100-1kohm in series with the lead 
>> to the
>> >switch.
>> >
>> >
>> >_______________________________________________
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>> >
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