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DPRG: 80C51FA for the New Micro's NMIY-0031 SBC (!!! or ???)

Subject: DPRG: 80C51FA for the New Micro's NMIY-0031 SBC (!!! or ???)
From: Kipton Moravec kmoravec at airmail.net
Date: Sun Jul 20 22:56:07 CDT 1997

O.K. Found the extractor in my Digikey Catalog. Thanks Eric.  Am I going
to need an inserter too?  I will get the extractor on order in the
morning.  I guess the only way to get experience is to bust up a couple
in the learning process. :(

I found the crystal in the schematic they provided it is a standard
11.0592 MHz as I expected.  What is curious for me is that while they
have the 22pF capacitors on both sides of the crystal going to ground
like the Intel book shows, they also have a 10 M Ohm resistor across the
crystal.  Has anyone seen that before, and why would you want to do
that?

As for going to the 14.7456 MHz crystal I will probably go to it later. 
Right now the monitor ROM that they gave me, would probably set the
communication rate from the current 9600 to 12800.  My PC does not talk
that speed to download SW. Oh by the way, 14.7456 MHz is about 33%
faster than 11.0592 MHz, not 50% faster. :) (But what are a few
percentage points between friends.)

For the lurkers curious about going faster than 11.0592 MHz, based on
the crystals I could find in the Digikey Catalog, 11.0592 MHz, 14.7456
MHz, 18.432 MHz, 22.1184 MHz all can do exactly 9600 baud. There are
other clock speeds that can get 9600 baud with the parameters you can
set, but I did not see them in the catalog.  Perhaps I will do a
tutitorial on the 8051 family serial port one day, if there is any
interest.

I continue to get more and more ideas what I want in my own 8051 based
board design. (And what I do not want!)

Thanks again for the info Eric.
Kip 

Eric B. Olsen wrote:
> 
> Kipton Moravec wrote:
> > I have the New Micro's NMIY-0031 single board computer.  Has anyone
> > tried to replace the 8031 with a 80C51FA?  It appears they have the
> > identical pin out. (At least from looking at the Intel book, they have a
> > Siemens chip installed). The 80C51FA has PWM for motor control (up to 4
> > separate PWM types), a counter geared towards optical encoders, and a
> > very accurate event timer (perhaps for acoustic distance detection). Oh
> > by the way, the 80C51FA has 256 bytes of data RAM also, versus the 128
> > bytes in the 8031. I think the 80C51FA costs less than $10 versus the
> > 8031's $3.
> >
> > Has anyone tried to pull the processor out of the holder successfully
> > (meaning without damaging anything). It appears to be a PLCC package and
> > chip holder.  I am not familiar with the process.
> >
> > Regards,
> > Kip
> 
> Kip,
> 
> One of the main advantages with the 8031/8051 Intel architecture is the
> existence of so many good derivatives offerd by third party
> manufacturers.  Even Intel has it's share of decent derivatives like the
> 80C51FA.
> 
> The main hardware difference that could stop one from using an 80C51FA
> instead of an 8031 is IF an external clock source is used to drive the
> CPU instead of using a crystal.  If a crystal is used on the New Micro's
> board (and I'm betting it is), there shouldn't be any problem at all.
> 
> Some 8031 designs use the lower cost NMOS chip as opposed to the modern
> CMOS version chip (80C31).  If an external clock is used to drive an
> NMOS 8031 CPU, the clock source is input to the XTAL2 input.  It appears
> that all subsequent 80C51 and later designs use the XTAL1 input for
> external clock drive.
> 
> Again, if a crystal oscillator is used (instead of an external clock),
> then your substitution should work just fine.
> 
> There are versions of the 80C51FA that run faster (up to 16 Mhz), and it
> you have one of these, you may consider changing the crystal frequency
> to get the extra horsepower!  I find that 14.7456 Mhz crystals are a
> good choice for 16Mhz type 80C51 parts as they are capable of producing
> standard baud rates, and are about 50 % faster than the 11.0592 Mhz
> crystals.  However, if you change the board frequency, factory ROMed
> software will not communicate at the correct speed!
> 
> Pulling out PLCC chips from their carriers can be tricky.  If you
> attempt to pry out the part using a screw driver at the corner of the
> socket, you will almost certainly damage the socket and possibly bend
> pins on the chip.  Use a PLCC extractor tool!  Digi-key offers a
> universal extractor tool for $19.95 (K293-ND), and a low cost universal
> extractor for $7.95 (although I haven't tried this one).  Even with the
> tool, a bit of tugging and a little expereince is beneficial!
> 
> Good Luck,
> 
> Eric Olsen
> Las Vegas, NV

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