Is an 8031 the best candidate for this idea?

[FalloutBoy]

Hi,

I have just started working on and idea for a RAM based Eprom emulator.
My idea is to have an 8031 copy data from an SD Card into two ram chips which would be pin compatible with the ROM's used in the system - obviously this circuit would be separately powered from the computer itself.

Doubts that I am having, and please bare in mind I am completely new to the world of electrik-ery.
Is the 8031 the right IC for the job, i have seen an 8051 connected to an SD card ( 8051 = 8031 with built in ROM ). I don't even know at this point if there would be enough connections on the IC to support - It's own ROM, the SD Card as well as what would be required to write to the ram chip.
I chose the 8031 because I got given a dozen of them for nothing

How would I and indeed would I need to refresh the ram which I am writing to or is there a type of ram which does not require refreshing ?

When the system is powered on with the Emulator in place will it hurt anything to have power coming from two sources I.E the 5v rail of the PC and the emulator itself's 5v line?

What I have managed to figure out so far.
The necessary voltage division to take 5v to 3.3v for the SD Card .

I do have some PIC18F4620's and a couple of Arduino's but would like to used the more outdated hardware first if at all possible.

Thanks in advance for those who reply.

 

[FvM]

An EPROM emulator design will primarly implement a number of multiplexers or tristateable buffers to switch the RAM lines (address, data, oe, cs) between target processor and loader logic. The loader logic can be either hardwired and e.g. implement a serial or parallel interface to a host computer or a microcontroller. There aren't much specific requirements for a processor in this role, it's more a matter of your personal preference. Basic 8031 had it's good times 20 or 30 years ago, I think. But of course it can be used.

Personally I stopped using EPROM emulators about 15 year ago, replacing the EPROM in respective processor systems by flash memory with bootloader software or switching to processors with internal flash. If I had to design a new one, I would use a 5V-tolerant CPLD to place all supporting logic in a single chip.

 

[betwixt]

Agreed, and the 8031 is now a very old device (1987 I think) and needs more support circuitry than modern processors. It is nice to use 'older' technology, especially when it is already there in front of you but in this instance the size and power consumption have to be taken into account so I would go for something newer.

Brian.

 

[phongphanp]

I think 8088 or 8086 is a good choice because there are many book support rather than the datasheet collection.
The Intel Atom board is nowadays technology is also more interesting .

 

[Gorgon]

I suppose it all depends on the specification on your emulator. You don't need to refresh the RAM if you use static RAM chips. The 8031 has a 64k address range, and if you need to use larger RAM chips, you'll also need to make a paged RAM system for the writing. Since the 8031 only has 128 bytes RAM itself, you may need to add extra RAM as well as EPROM/Flash for the program.
The SD interface is also a consideration in this picture.

All in all, I think I would recommend a more updated part for this project.

You can use the 8031 to simpler tasks, and maybe this would be a better learning experience if you are new to the game.