External Memory Bus for 8051

[Andy Roark]

Hello everyone,

Can anyone direct me toward a schematic/instructions for setting up an
external memory bus from Port 0/2 of an 8051 mC. I am pretty sure I
am going to use a 373 latch, a 28C64A EPROM and a 22V10. Again, i'm
pretty sure i'm almost there but this is my first one and would like
to compare what I have drawn out with something else before I break
out the wire wrap tool.

Thanks for any help.

 

[Ken Smith]

Hello everyone,

Can anyone direct me toward a schematic/instructions for setting up an
external memory bus from Port 0/2 of an 8051 mC. I am pretty sure I
am going to use a 373 latch, a 28C64A EPROM and a 22V10. Again, i'm
pretty sure i'm almost there but this is my first one and would like
to compare what I have drawn out with something else before I break
out the wire wrap tool.

What's the 22V10 for?

Why not a HCT273 instead of the 373?

Why not a 27C512 socket with the needed option jumpers for 28C64, 27C128
etc?


Why not also make it take 2 chips, static RAM and a PROM? If you do, I
can think of a used for the 22V10. You can make it so that the RAM can be
switched in and out of the code space.

 

[Anthony Fremont]

Hello everyone,

Can anyone direct me toward a schematic/instructions for setting up an
external memory bus from Port 0/2 of an 8051 mC. I am pretty sure I
am going to use a 373 latch, a 28C64A EPROM and a 22V10. Again, i'm
pretty sure i'm almost there but this is my first one and would like
to compare what I have drawn out with something else before I break
out the wire wrap tool.

Thanks for any help.

Check out the 74xx573 instead of the 373, you may like the pinout
better.

Look here for 805x stuff:
www.8052.com

 

[Pooh Bear]

Hello everyone,

Can anyone direct me toward a schematic/instructions for setting up an
external memory bus from Port 0/2 of an 8051 mC. I am pretty sure I
am going to use a 373 latch, a 28C64A EPROM and a 22V10. Again, i'm
pretty sure i'm almost there but this is my first one and would like
to compare what I have drawn out with something else before I break
out the wire wrap tool.

You just want the memory bus to access an Eprom?

You only need the latch and the Eprom. Dunno what you reckon you need a
22V10 for.

You know you can get 8051 variants with plenty of on-board ROM these days
and that frees up loads of the pins for general purpose I/O.


Graham

 

[Andy Roark]

Thanks for the link.

Also thanks for the suggestions. I'm afraid I am still in school and
many of the parameters of the project are already set. I have to use
the latch/rom and the 22V10 to handle the address bus and interface
all of my external components through that bus. Yes, we are using
older parts but such is the norm in education I think. Plus they are
cheap to replace when I blow them up.

Primarily I was looking for information on the basic layout (I found a
pretty decent schematic) and also information on exactly how to
interface the LCD/Keypad/etc back to the bus.

The www.8052.com website was very helpful. Thank you for providing
it.

Andy

 

[martin griffith]

Thanks for the link.

snip.
Yes, we are using

older parts but such is the norm in education I think. Plus they are
cheap to replace when I blow them up.

ARGHH...
You are still using EPROMs? what a waste of time, 20 min erase cycle
IIRC. How long is a lesson these days, maybe 3 or 4 erase cycles.

Sorry but I think it is utterly STUPID to use EPROMs when you can
burn a flash 8051 8K in 30 seconds or so. Tell the teacher I said so!
(sorry for the rant)

Primarily I was looking for information on the basic layout (I found a
pretty decent schematic) and also information on exactly how to
interface the LCD/Keypad/etc back to the bus.

The www.8052.com website was very helpful. Thank you for providing
it.

Andy

martin


"Facts are stupid things.." -- Reagan, '88

 

[Ken Smith]

Sorry but I think it is utterly STUPID to use EPROMs when you can
burn a flash 8051 8K in 30 seconds or so. Tell the teacher I said so!
(sorry for the rant)

Better yet, hook up a static RAM so you can run out of it.

You could then download the program and have it crash in under 10 seconds.

 

[Nicholas O. Lindan]

[Help with 8051/external mem. school project]

You are still using EPROMs? what a waste of time, 20 min erase cycle
IIRC. How long is a lesson these days, maybe 3 or 4 erase cycles.

One EPROM,
One EPROM,
You gets no joy with _one_ EPROM

Most folks have more than one available, they all get erased together
over lunch, etc..

Sorry but I think it is utterly STUPID to use EPROMs when you can
burn a flash 8051 8K in 30 seconds or so.

Is that a fact?

"Facts are stupid things.." -- Reagan, '88

As a learning exercise hooking up external memory to an 8051 is a
good choice. Burning invisible [to the student] buried flash memory
teaches very little. I think the EPROM way is a good idea, and you
can tell the teacher I said so.

 

[martin griffith]

[Help with 8051/external mem. school project]

You are still using EPROMs? what a waste of time, 20 min erase cycle
IIRC. How long is a lesson these days, maybe 3 or 4 erase cycles.

One EPROM,
One EPROM,
You gets no joy with _one_ EPROM

Most folks have more than one available, they all get erased together
over lunch, etc..

Sorry but I think it is utterly STUPID to use EPROMs when you can
burn a flash 8051 8K in 30 seconds or so.

Is that a fact?

"Facts are stupid things.." -- Reagan, '88

As a learning exercise hooking up external memory to an 8051 is a
good choice. Burning invisible [to the student] buried flash memory
teaches very little. I think the EPROM way is a good idea, and you
can tell the teacher I said so.

Hi Nicholas.

I used to use many UV EPROMS for 8051's in the pre flash days, and I
used to get utterly frustrated with stuck bits etc. I had assumed that
the schools was still using UV Eproms, not EEproms.

If the school is using EEproms I stand corrected, but if they are
using UV Eproms, I think I will stand by my comments, and apologise to
the teacher

But once student can hand wire, on say strip board, up a memory mapped
device and fault find it, surely it is time to move on to flashed
products, and get onto programming, which is probably the idea of the
lessons, rather than fault finding all those address and data busses.

Anyway its great to hear that schools are teaching microprocessors,
rather than just Windoze apps.

martin


"Facts are stupid things.." -- Reagan, '88