RAM Memory Viewer Reader Chip?

[YoshiMoshi]

TL;DR Summary

A chip that will output it's memory, please help

I'm working on a project for fun. I have a parallel external work RAM chip on a old console, whose datasheet is online.

I'm thinking of disassembling the console and making my own circuit with the parts. I was hoping to create a circuit that can "watch" the data as it's being written onto the default RAM chip that came on the console. Essentially something like this.

Where the chip (?) I'm looking for would be connected to the same RAM data bus, that would output the memory map live onto a personal computer.

So essentially when the CPU writes data to a specific address on the EWRAM chip I can see the address get updated on my personal computer as well and can watch it happen live.

I could go the long road of trying to design something on my own with a microcontroller, but am wondering if a commercial product like this exists as an IC

Please and thanks.

 

[DaveE]

I think you are describing a logic analyzer. You can buy them. For an older system, I'd guess a cheap eBay version would work well enough. Then maybe you can use it again on your next project. Often the hard part is making all of the connections.

I'm not sure you'll get the "memory map" just by looking at the data on the buss, you might not know what it means without knowing the source code. Or maybe my idea of a memory map is different than yours.

Also, maybe it's just me, but I have no idea what an "external work RAM chip" is. Do you mean a flash drive (external storage)?

Finally, if you want useful advice, tell us more. What sort of system, what kind of bus (serial parallel, etc.), what data rates (clock speed), etc. This is all way to vague at this point; EEs nearly always work with detailed information since there are so many possibilities out there.

 

[Rive]

Some game console, I guess?

There are several issues with the project.

- The trivial solution (as @DaveE mentioned - a logic analyzer) is either cheap and has limited capabilities (due USB connection) or they are ... well, just not in reach usually.
- The non-trivial solution means quite decent knowledge on PCs and their interfaces, both HW ans SW level
- Due the compact design you'll need to manufacture special cables to properly access te device without interfering its workings
- the analyzer will produce immense amount of data and you'll need some really good visualization strategy and programming skill to have anything nice coming out of it...

I would rather pick an old Commodore thing. More information, more access and it's slower = far more doable.

 

[YoshiMoshi]

Yes a GBA

It's a parallel ram chip. It's referred to as external work RAM in literature I see, most likely to differentiate it from the internal RAM ok the CPU.

I know about logic analyzers, just wondering if there was something that would take the data from it and put it in a memory map, showing the address locations and the data currently on it.

One pin tells it to read or write. There are parallel address lines, and parallel data lines.

Essentially something that will see when data is written to it, what address is be called, and war data is written at that specific location. I know a logic analyzer will produce lots of data, just wondering if there's a specific application for a PC or a piece of hardware that will take that data and put it into a nice list, essentially allowing visualization of what data is at what address, live.

I know I can use a logic analyzer, visually see the write pin go high, see what address lines are being called, and what data is being sent on the data lines, just wondering if there's something that would produce a nice list as a memory map for me to visualize this data.

 

[YoshiMoshi]

Any ideas?

 

[Baluncore]

Use a logic analyser to track the memory data transfers.
Read that data into a PC.

Use an integer array in the PC to build a memory image.
First, mark all array elements as being invalid data.

Analyse each data transfer for address and data.
Extract the bus address and data for each read or write transfer.
Write that data into that address in the image array. Mark valid.
Repeat until all transfers done, many will be over-writes.

Hexdump the memory image array.
Valid entries show the latest data values in the RAM.

You might also count the reads and the writes to each location, in another array. That would also indicate valid data.

 

[YoshiMoshi]

Hey thanks. Any commercial product that already does this all for me?

 

[Baluncore]

Any commercial product that already does this all for me?

No.
You buy the logic analyser and connect to the target CPU bus.
You plug the logic analyser into your PC USB port.
You look at the data transfer files on your PC, then decide to program your PC to show the result in a more readable form.

What is the CPU that you will monitor?
What is the RAM chip you want to watch?

Maybe; 16 address + 8 data + 3 control = 27 bits, or channels.
Look for a 32 channel logic analyser, with USB interface, on eBay.
Maybe a Hantek 4032L will do the job.
Expect to pay a few hundred US$.

 

[Averagesupernova]

No.
You buy the logic analyser and connect to the target CPU bus.
You plug the logic analyser into your PC USB port.
You look at the data transfer files on your PC, then decide to program your PC to show the result in a more readable form.

What is the CPU that you will monitor?
What is the RAM chip you want to watch?

Maybe; 16 address + 8 data + 3 control = 27 bits, or channels.
Look for a 32 channel logic analyser, with USB interface, on eBay.
Maybe a Hantek 4032L will do the job.
Expect to pay a few hundred US$.

@YoshiMoshi the above is what engineers do. There is not an endless supply of ready made solutions to what is needed in engineering. Circuits are built, code is written, etc., just as tools used to troubleshoot or develop other circuits and/or products.