External Memory Bus for 8051

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.

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

Look here for 805x stuff:

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

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

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

Andy

snip. Yes, we are using

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)

martin

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

In article , martin griffith wrote: [...]

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.

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..

Is that a fact?

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