my microcontroller board has installed a 23256AC (i.e. 27c256
style) ROM chip with 8031 MCU...
I traced the ROM chip's pins to be (reasonably) sure that i was
selecting a correct/compatible eprom chip setup for ***reading***
this ROM chip on an e(e)prom programmer, as the programmer did
not show direct sup****t for the chip.
When tracing connections i found that (pin 1 - NC) on the chip
was tied to (pin 27 - A14) and these connected to (Addr 14) on
the MCU
is there a design reason for doing that, maybe prevent using a
27c512 chip for example ?
so for different ROM chips that means that
Chip Pin 1 -> Pin 27 = ?result/purpose?
--------------------------------------------------------
23128 NC -> PGM = no prob
27c128 Vprog -> PGM = ???
23256 NC -> A14 = no prob
27c256 Vprog -> A14 = ???
27c512 A15 -> A14 = **???
-------------------------------------------------------
Does this mean i can not use a 27c512 chip ?
or maybe it is a simple way to prevent a floating address line ?
any ideas on this greatly appreciated,
robb
