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Newbie question regarding data offsets on an EPROM.

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BarkingMad

New Member
Hi there,

I have a quick question for you regarding data offsets on an EPROM chip that I hope you can help with...

I currently have data stored on an EPROM from hex 8000-FFFF, what I would like to do is use 1 8000-1 FFFF for a different set of data. The data sheet says I have an address data latch "When CE is low and ALE is high the address from input buffer is transfer to address decoder by falling edge of ALE". :?

Does that mean that I can run 5v (through a 10k?? resistor) to the ALE pin and it will offset the data to the 1 8000 address range? or would there be a way of altering the signal through A16 which is the Address line.

Many thanks...


 

laroche73

New Member
address

No, the address latch enable (ALE) line validates the address on pins A0-A16 for the EPROMs' internal decoding circuitry. You need to pull A16 (and A15) high to use the upper address bank (i.e. A16 is the "1" in 1 8000H to 1 FFFFH). A low on A16 (and a high on A15) will access 8000H - 0FFFFH.
 

BarkingMad

New Member
Thats great, many thanks for the advice. Can I please show my true colours as an electronic dud and ask another stupid Q? :oops:

The above circuit is an automotive ecu that uses an eprom with the lower address range for its data. I am trying to utilize the upper address range to squeeze a second set of maps on it.

A15 will currently be high... all I need to do is switch A16 high. Is it as simple as soldering a wire from A16 to Vcc via a switch? and do I need an inline resistor.

Cheers,
 
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