EPROM Emulator Proposal

[Squash]

Ah yes.  This makes sense now.  I think that i would
use the emulator for tuning and then "burn" an eeprom
or eprom to stick in the memcal itself.  It would
simplify things to just swap that in if anything fails
in the emulator, IMHO.

Wouldn't just the CS/CE on the DPRAM would need to be
isolated during the power cycles?  If no CE, no write,
correct?

Andy

--- thergen at svn.net wrote:
> Battery backed rams I've used have usually been very
> picky about the
> states of chip selects during
> power-up/power-down/power-off.  It's very
> easy to do an accidental write to an arbitrary
> location.  Often, chip
> selects and write enables are active low.  Low is
> where all the signals go
> during power-down (hence the need for the special
> handling of chip
> select).  Chip select level(s) during power off may
> also determine whether
> or not the lowest power state is entered which can
> severly affect backup
> battery life.
> 
> Tom
> 
> On Wed, 7 Apr 1999, Squash wrote:
> 
> > But if dpram is battery backed, there should be no
> > need for a weird circuit on power-up, right?  It
> would
> > act just like an eeprom?
> > 
> > Andy
> > 
> > --- thergen at svn.net wrote:
> > > I think it's a good proposal.  I'd like to
> suggest
> > > that a pushbutton
> > > switch be part of the design that can be used to
> > > reload the default dpram
> > > bank from the eprom (assuming it's present) so
> that
> > > you can recover from a
> > > corrupted ram image without using a laptop
> computer.
> > >  Power-up/power-down
> > > need special attention (as you already know) to
> > > avoid corrupting the ram. 
> > > Maxim (www.maxim-ic.com) and others make parts
> with
> > > voltage supervisors
> > > specifically for memory protection (let me know
> if
> > > you want specifics). 
> > >  
> > > Tom
> > >  
> > > On Wed, 7 Apr 1999, Ludis Langens wrote:
> > >  
> > > > The EPROM emulator debate on this list seems
> to be
> > > going in circles.
> > > > Either people have short memories, or there
> are a
> > > lot of new members who
> > > > missed the discussion and decisions made in
> the
> > > first few weeks of
> > > > gmecm.  Either way, please read through the
> > > archives.
> > > >
> > > > Anyway, here is an emulator proposal based on
> the
> > > prior discussion.  I 
> > > > did some ruthless cutting of features and
> > > expandability (indicated with
> > > > a *).  I propose the use of a single dual-port
> > > SRAM (from Cypress or  
> > > > IDT) and a 40/44 pin PIC microcontroller to
> load
> > > this RAM.  A battery 
> > > > back up will keep the SRAM alive.  This allows
> an
> > > ECM to boot from the
> > > > DPRAM immediately upon power-up.  The whole
> > > emulator circuit board  
> > > > should be small enough to fit inside a
> > > '165/'727/'730/'749/'808 ECM.
> > > ....
> > > 
> > > 
> > > 
> > > 
> > 
> >
>
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> 
> 

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