switching between EPROMS

[fontana pasquale]

Hello Warren 

To switch  two eprom or two different bank (range address) of memory the
problem is the

same : you must disable your ECU then change and after rearm your SYSTEM.

In other word , you must go off the ENGINE then switch.

The problem for to make a change when the engine is running is very very
complex.

I think you dont need the opportunity to switch your ECU  when is running .

In this case is necessary a simple switch for to controll the CS (chip
select) and the 

OE (output enable) for the two device: when first is ON the second must be OFF .

The problem is very semplified if you use a device who is 2X of memory .

EX for to switch two 27128 chip you must have a 27256 and controll the pin
for the MSB

A15 (if i remember) .

If you want to use the first bank this pin must to be " 0 " (ground ) for
the second

" 1 " (+ VCC ) .

BYE Pasquale
   




 

 
>Hello All,
>
>quick question:
>
>has anyone made a device that you can plugs lots of EPROMs into, plug into
>your car ECU, and switch between them with a switch??
>
>I want to make one for only 2 EPROMs, and was thinking of using a simple
>switch to switch the chip enable between the EPROMs.  Will this work?? or
>will the time gap when neither of the EPROMs are enabled be enough to
>confuse the micro, and go into some unknown state?  
>
>I could use latches and some simple logic chips to get around this I guess.
>
>Any recommendations??
>
>Warren
>_______________________________________________________________
>Warren Crowther      
>Software Engineer    			  DDI +649 3610625
>warren at advgroup.co.nz        		  Ph  +649 3602834 x5625
>Advantage Systems Ltd                     Fax +649 3764210
>   	
>
>
>