>This is not only off topic, but probably a question WAY below the level of
> expertise of the majority of the group.  I haven't found a difinitive answer
> anywhere, so I'm turning here.
>
>My question is about EPROMS.  In a project I'm making I need to interface a set
> of digital lines to a 14 segment display.  The only problem is this... The
> lines are not your normal hex.  They have a funky logic.  I could use a bunch
> of gates and make the output I want, or I could use a PGA.  Neither of which
> are very good solutions for the small size of this application.
>
>I was wondering if I could use an EPROM in this way.  Put the input into the
> address lines and feed the 14 segment display off the output lines.  Would
this
> be possible?  I know EPROMS are slower than other ICs, but am I going to be
> able to use this to multiplex displays?
1970s, 1980s digital boards commonly had PROMs that did such lookup
tables, and state machine sequencing, before the days of bit slices, PALs
and microcontrollers.  We use little lookup ROMs all
the time in our ASICs, for sin/cos tables, filter coefficients, etc.  blah blah
>
>Also, can I drive the display directly from the outputs of the eprom, or do I
> need to use transistors?
If an LED is hooked to 5V via a 470ohm resistor (a typical value, I think),
it is
drawing about 5/470 = 11mA and is bright enough to see.  PICs can drive
20mA, and can directly drive LEDs, but I think EPROMs don't have as hefty
output drivers.  Ya have to check the spec sheet.  If I remember, many
FLASHes (similar)
have on the order of 50mA MAX supply current, which would be too close..
You can probably
use an integrated driver chip with all the transistors on it..
>
>Thanks for being patient.
Quit apologizing!
>Terry Ewing
>