9 Nov
1998
9 Nov
'98
4:05 p.m.
Ethan wrote:
I am not sufficiently versed in flash chips to
consider designing one
in. I am sufficiently well versed to include a 27xx EPROM. It's not
the original 32x8 PROM, but it's close enough.
There are two kinds of Flash chips; the older kind need a 12V programming
voltage; the newer ones use a single supply. I wouldn't mess with the
former.
Although there are some software complexities, the hardware support needed
for the single-supply Flash parts is simply providing a WE signal, just
like for an SRAM (but on a different pin, IIRC).
Many boards are designed with footprints that can be jumpered for SRAM,
EPROM, or Flash. At this late date, I wouldn't even worry too much about
EPROM.
The most common 8-bit 5V-only flash parts I know of are the AMD Am29F010
(128K*8) and the Am29F040 (512K*8). Either one is obviously overkill for an
ELF clone, but I don't think you can get the smaller ones any longer.
The last time I priced them, the Am29F040 was under $10 in small quantities;
perhaps the Am29F010 might even be under $5.
Cheers,
Eric