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We have been using a DC-DC converter that supplied a power-ok signal
when the 5v output was stable, this was used to control the 9s12xDP512
reset line. We now are going to a 3.3v DC-DC converter that does not
have this power-ok signal.

Would a simple resistor and capacitor RC network a reasonable solution
for the reset line? If so what values would be a good choice? Or
should we go to a dedicated reset IC and does anyone have one that
they would recommend. Thanks in advance for the advice.

Robert Lewis



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--- In 6...@yahoogroups.com, blewis999 wrote:

> We have been using a DC-DC converter that supplied a power-ok signal
> when the 5v output was stable, this was used to control the 9s12xDP512
> reset line. We now are going to a 3.3v DC-DC converter that does not
> have this power-ok signal.
>
> Would a simple resistor and capacitor RC network a reasonable solution
> for the reset line? If so what values would be a good choice? Or
> should we go to a dedicated reset IC and does anyone have one that
> they would recommend. Thanks in advance for the advice.

It appears it is always best to use a reset chip on these devices.
If you have a search through the old messages you will find some solid info on the whys' and wherefores of devices to choose.

There was good advice, like don't use open collector, use a readily available and second sourced one, preferably cheap etc.

I think it was Doron who advised on the LM809 M3, this was as always excellent advise from him, it was the last time we had a reset problem.
The only problem was that they are hard to come by over here in small qttys, reels only, made the prototype more expensive then anticipated.

Not sure what is appropriate for 3.3V, but for our 5V units we choose a 4.6V trip point, worked well, although for our next design we dropped that to 4.3 due to poorer regulation of the power supply.

Cheers,

Theo





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On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
> There was good advice, like don't use open collector, [...]

Are you sure that one should not use open collector? I would think
that an open drain/open collector output would be essential, since
the HC12's reset line is both an input and an output.

I don't recall this aspect of the earlier conversation, so I'd
appreciate a refresher from anyone who remembers.

Stephen

--
Stephen Trier
Technical Development Lab
Cleveland FES Center
s...@po.cwru.edu




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If you're really having trouble with the reset circuit, try the Maxim
DS1233 that is pin-pin compat with the 33064, but has a 350 ms reset time.
S. Prince

Stephen Trier wrote:

>On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
>
>
>>There was good advice, like don't use open collector, [...]
>>
>>Are you sure that one should not use open collector? I would think
>that an open drain/open collector output would be essential, since
>the HC12's reset line is both an input and an output.
>
>I don't recall this aspect of the earlier conversation, so I'd
>appreciate a refresher from anyone who remembers.
>
> Stephen
>
>
>
[Non-text portions of this message have been removed]





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Stephen Trier wrote:

> On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
> > There was good advice, like don't use open collector, [...]

Theo: that was not really an advice (at least not from me), OC is
fine, but push-pull *809 is better available in my experience.

> Are you sure that one should not use open collector? I would think
> that an open drain/open collector output would be essential, since
> the HC12's reset line is both an input and an output.

Use a resistor between the push-pull reset output and the HC(S)12
Reset pin. Please note that you must not use pullup resistors on the
reset line then - this resistor replaces the pullup!

Oliver
--
Oliver Betz, Muenchen



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On Wed, Jul 12, 2006 at 04:12:54PM +0200, Oliver Betz wrote:
> Use a resistor between the push-pull reset output and the HC(S)12
> Reset pin. Please note that you must not use pullup resistors on the
> reset line then - this resistor replaces the pullup!

That makes a lot of sense. Thank you, Oliver.

Stephen

--
Stephen Trier
Technical Development Lab
Cleveland FES Center
s...@po.cwru.edu


______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


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--- In 6...@yahoogroups.com, "Stephen Trier" wrote:
>
> On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
> > There was good advice, like don't use open collector, [...]
>
> Are you sure that one should not use open collector? I would think
> that an open drain/open collector output would be essential, since
> the HC12's reset line is both an input and an output.
>
> I don't recall this aspect of the earlier conversation, so I'd
> appreciate a refresher from anyone who remembers.

It is some time ago this was debated, i.e. when I had to make the choice.

PP is better for a couple of reasons, most importandly for small manufacturers these devices are readily available from many sources.
There is no problem when you make a million units, they will divert some foundry output for you.
For me it needs to be available in one reel lots and preferably in a few ofs from RS and co for prototype and emergencies.
That said I always feel more secure when devices drive in both directions, any impedance problems will be likely due to the series resistance:-)
Cheers,

Theo



______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


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--- In 6...@yahoogroups.com, Dr Stewart Prince wrote:
>
> If you're really having trouble with the reset circuit, try the Maxim
> DS1233 that is pin-pin compat with the 33064, but has a 350 ms reset time.
> S. Prince

Are these devices second sourced?

And why 350mS, slow poer supply?

Cheers,

Theo
> Stephen Trier wrote:
>
> >On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
> >
> >
> >>There was good advice, like don't use open collector, [...]
> >>
> >>
> >
> >Are you sure that one should not use open collector? I would think
> >that an open drain/open collector output would be essential, since
> >the HC12's reset line is both an input and an output.
> >
> >I don't recall this aspect of the earlier conversation, so I'd
> >appreciate a refresher from anyone who remembers.
> >
> > Stephen
> >
> >
> >
> [Non-text portions of this message have been removed]
>





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--- In 6...@yahoogroups.com, "Oliver Betz" wrote:
>
> Stephen Trier wrote:
>
> > On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
> > > There was good advice, like don't use open collector, [...]
>
> Theo: that was not really an advice (at least not from me), OC is
> fine, but push-pull *809 is better available in my experience.

It is some time ago and memory is not wath it used to be, sorry to bandy your name about, maybe try Doron:-)
But yes, I agree, push pull is best.

> > Are you sure that one should not use open collector? I would think
> > that an open drain/open collector output would be essential, since
> > the HC12's reset line is both an input and an output.
>
> Use a resistor between the push-pull reset output and the HC(S)12
> Reset pin. Please note that you must not use pullup resistors on the
> reset line then - this resistor replaces the pullup!

Yup, and same impedance both directions...

Cheers,
Theo



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theobee00 wrote:
> --- In 6...@yahoogroups.com, "Stephen Trier" wrote:
>
>>On Tue, Jul 11, 2006 at 09:39:53PM +0000, theobee00 wrote:
>>
>>>There was good advice, like don't use open collector, [...]
>>
>>Are you sure that one should not use open collector? I would think
>>that an open drain/open collector output would be essential, since
>>the HC12's reset line is both an input and an output.
>>
>>I don't recall this aspect of the earlier conversation, so I'd
>>appreciate a refresher from anyone who remembers.
> It is some time ago this was debated, i.e. when I had to make the choice.
>
> PP is better for a couple of reasons, most importandly for small manufacturers these devices are readily available from many sources.
> There is no problem when you make a million units, they will divert some foundry output for you.
> For me it needs to be available in one reel lots and preferably in a few ofs from RS and co for prototype and emergencies.
> That said I always feel more secure when devices drive in both directions, any impedance problems will be likely due to the series resistance:-)
> Cheers,
>
> Theo
>
>



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Robert Mitchell wrote:

[...]

> I am not sure why Oliver recommends the devices with active pull-up. In

I explicitly didn't _recommend_ them. I wrote that they can be used
and are simpler to get than OC types.

> many of the processors produced recently there is already a pull-up
> built into the chip and it is not necessary to have any reset device
> unless the system is open to FLASH corruption on power-down. Rise time

Last time I observed this with a HC912D60A. As long as I'm not sure
that the 9S12 is better, I will use a delayed reset circuit with 9S12
chips.

> on the reset line is generally not an issue, there is hysteresis to
> avoid any possibility of oscillation if the rising edge is slow (within
> reason).

The issue might be the slow start of the Colpitts oscillator.

> Because of any in-built pull-up, there are limitations on the size of a

which 9S12 has an pullup resistor on the reset pin?

> Despite having looked at a lot of the alternates to the MC33064/MC33164
> devices I have always ended up using these devices without problems. The

The last time I used the 33064 successfully was with HC11
derivatives. Well, _that_ was the last robust chip from Motorola with
well-known bbehaviour.

Oliver
--
Oliver Betz, Muenchen



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I need to implement some SDLC communications and I would like to use
the HC12 because I am already familiar with it, have all the debug tools
etc ...
Anybody have any good ideas how to do this ? I have looked for some sort
of SDLC transceiver / translator chip but haven't had any luck. Any
comments
would be appreciated.
Thanks,
Jeff




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How about a zilog 8530 scc?

-----Original Message-----
From: j...@atsi-tester.com
To: 6...@yahoogroups.com
Sent: Tue, 18 Jul 2006 1:28 PM
Subject: [68HC12] OT - SDLC Communications
I need to implement some SDLC communications and I would like to use
the HC12 because I am already familiar with it, have all the debug tools
etc ...
Anybody have any good ideas how to do this ? I have looked for some sort
of SDLC transceiver / translator chip but haven't had any luck. Any
comments
would be appreciated.
Thanks,
Jeff



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