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In article <7266@darkstar.ucsc.edu> lance@helios.ucsc.edu (Lance Bresee) writes:
>
>I am having trouble hooking up
>an 8049 to a 2764 EPROM.  I hooked
>up a 74373 latch with latch and 'OE
>tied directly to ALE, and the 'CE and 'OE
>of the 2764 hooked to 'PSEN.  The program
>should alternately output 00h and FFh on
>port 1, with a significant delay.  The output
>of port one is connected directly to led's.
>
>Does anyone out there have any schematics
>of a known working, simple, 8048 device
>that I can look at?
>
>Thanx muchly
>lance%helios@ucscc.ucsc.edu

As you aren't too specific on what exactly the problem is, I am
assuming that you've debugged your program 'on-the-bench' and the
logic looks right but when you burn an EPROM and power your
system up it just sits there. Your EPROM hook up sounds right
except, did you bring the EA pin (External access, pin 7) high
(tie to Vcc) ?  Without this pin wired high the 8048 will be
executing internal ROM code, not your EPROM code. Also check that
the RESET line is asserted high (a simple RC circuit is all that is
needed).

Good references to 8048 'projects' are Intel Databooks, BYTE
circuit Cellar projects and Circuit Cellar Ink magazine.


				- Jeff

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