Gil Simon wrote:
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" all memories are faster than micros " so no need to worry about time for the instructions be fetched from the ext. code memory. But if the memory is slower than micro then it will slow down the program "

Right ?? is that you mean Peter.


Absolutely NO !!!

Today 8051 micros goes to be faster and faster (XTAL = 40MHz, cycle = XTAL / 4).
So most older EPROMs (120ns) are to slow today.
E.g. I need often faster than 55ns access time.


And if the EPROM to slow, then the program crash bum bang !!!

Using to slow EPROMs is a nice way to spend month over month to search a supposed software bug :-)


Peter