Al,, what value resistance for MSP430 outputs to TTL inputs?
I recall you mentioning 470 ohms to the gate of an FET, but
not to TTL.

Jack


--- In msp430@msp4..., onestone <onestone@b...> wrote:
> If you get really stuck email me. Up until I
sourced these parts I ran 
> all my displays on 5V, and just used current limiting resistors in the 
> I/O lines. These systems run 24 hours a day, and there are thousands 
> that have been running for 4 years now, so this is safe.
> 
> Al

Most of the Ti samples use 330R but I still use 470R. Theoretically this 
may not be considered adequate, since you need to drop 1.7V, and the 
protection diodes are rated at 2mA, thus you need around 750R, but I've 
never had a problem, and find this a good compromise.

Al

Jack wrote:

> 
> Al,, what value resistance for MSP430 outputs to TTL inputs?
> I recall you mentioning 470 ohms to the gate of an FET, but
> not to TTL.
> 
> Jack
> 
> 
> --- In msp430@msp4..., onestone <onestone@b...> wrote:
> 
>>If you get really stuck email me. Up until I sourced these parts I ran 
>>all my displays on 5V, and just used current limiting resistors in the 
>>I/O lines. These systems run 24 hours a day, and there are thousands 
>>that have been running for 4 years now, so this is safe.
>>
>>Al
> 
> 
> 
> 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 

On Sun, Nov 21, 2004 at 03:19:33PM +1030, onestone wrote:

> Most of the Ti samples use 330R but I still use
470R. Theoretically this 
> may not be considered adequate, since you need to drop 1.7V, and the 
> protection diodes are rated at 2mA, thus you need around 750R, but
I've 
> never had a problem, and find this a good compromise.

470R? This really works? The 3.5mA are able to rise the power supply
of the MSP430 above the 4.2volts allowed if it runs at low current (1uA)
and the 5V-output will stay at high for a long time. I would use 10k-100k
(but dont expect high speed).

In case of dot matrix LCD's this is not a problem. Only the databus is
a output and only for short time (reading busy flag).

M.

My reply was in response to an enquiry regarding an LCD, hence 470R is 
fine, even if you do use the busy flag, which I don't. If you read a few 
other posts I've made on the subject you'll find that I generally
don't 
mix 3V and 5V circuits, since everything I need, with a couple of sensor 
exceptions, is available in 3V. In addition, if you look back on the 
posts regarding 5V supplied to the micro you'll find that as far as can 
be discerned (ie it may shorten the life from 10 years to 9 years) by 
the many people who have done this, powering the micro from 5V, or even 
applying 5V to the I/O pins doesn't seem to have any lasting effect.

Obviously I don't recommend this. When I answer I answer from my own 
experiences and evaluations. I try to quote the specs, as I did in this 
post, but I believe that Ti are over conservative in many areas. The 
most glaring being the 3V6 spec for 8MHz.

I have a minimum of 16 designs in the field using MSP430s with an 
average of 2000 units per design. all but a couple of the designs have a 
5V LCD on them. Most of the designs were done before December 2000 (all 
but 4). I have not had a single PCB retunred with a failure. (software 
or hardware) From this I can only assume that I am doing something right.

Al

Matthias Weingart wrote:
> On Sun, Nov 21, 2004 at 03:19:33PM +1030, onestone wrote:
> 
> 
>>Most of the Ti samples use 330R but I still use 470R. Theoretically this

>>may not be considered adequate, since you need to drop 1.7V, and the 
>>protection diodes are rated at 2mA, thus you need around 750R, but
I've 
>>never had a problem, and find this a good compromise.
> 
> 
> 470R? This really works? The 3.5mA are able to rise the power supply
> of the MSP430 above the 4.2volts allowed if it runs at low current (1uA)
> and the 5V-output will stay at high for a long time. I would use 10k-100k
> (but dont expect high speed).
> 
> In case of dot matrix LCD's this is not a problem. Only the databus is
> a output and only for short time (reading busy flag).
> 
> M.
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 

On Fri, 2004-11-19 at 05:56, calin_dorohoi wrote:
> I have to interface with:
> 
> 1. An IR sensor.
> 2. An alphanumerical LCD display.
> 3. An IDE bus.

One of my projects requires some interfacing on the CompactFlash bus,
which can run either 3V3 or 5V depending on the host... So we use a
little level translator... the SN74LVCC3245. This little bugger will is
bidirectional and allows you to force the local bus side to one voltage,
and allow the bus on the "outside world" side to go to a different
logic
level...

Just in case the series I limiting resistors don't work for your
particular IDE bus...

Dave