Hi. I have no knowledge about anything going on here but need some guidance.
The chip MB90F553A is in an old rare broadcast monitor.
I would like to know if it is possible to dump the data on it and flash it onto a new chip.
Any help is appreciated, I asked in multiple places and I am not getting a proper response.
Let me have a look. Thank you for asking.
That looks like a hard one. The data sheets I find say it’s a proprietary 16bit microcontroller so there’d be no way to know what it does without ripping the code and knowing how to disassemble it for that chip.
Is there an overall larger goal?
Hi Ian. Many thanks for the response.
The JVC DTV series of CRT broadcast monitors is highly sought after by us in the retro gaming community as they output a very high quality and accurate analog display signal.
This IC is the cause of a lot of issues in this monitor as outlined in the service manual. I have one dead monitor that requires a replacement, and know several people in the community with the same issue.
The purpose of doing this is to provide the community with either a replacement part for their broken monitors, or write a guide on how to flash a replacement chip.
I’m reading more on the subject and just learned this chip uses the I2C protocol for communication. Since it’s proprietary, does this mean the data would be protected and cannot be dumped?
Thanks again
Edit: Please excuse my noob questions. Does the process require more than dumping and flashing to a new chip?
Sorry, my reply was lost somehow.
That sounds like an admirable goal.
The key is to find some documentation on how to read and write the chip, then if nothing is protected it is a simple matter to copy to a new chip. But that is only once you know how to actually read it.
Do you know if the chip is using I2C components, or is itself programmed with I2C?
if it is simply setting some I2C devices to eg tune channels, then you may be able to use a different chip for that. The key would be using a logic analyzer to capture the I2C bus during power up and tuning/volume actions, then send the same commands and see if it works without the chip.
This is entirely conjecture though. Finding datasheets for antique components can be challenging.
The bus Pirate probably isn’t what you need for this - the i2c bus is usually used to control peripheral chips.
It looks like you could read the chip with a basic programmer with the correct software.
How you proceed is down to how much time and money you can dedicate to it.
First thing is to find a way to program one… Then find a way to read it…
If you can’t program one, no point in reading it.
If you have the time, it could be possible to reverse engineer what it does in a more contemporary fashion - a rp2040 for example.
That way you are in complete control.
Unfortunately A lot of chips in such devices use mask roms - cheaper to manufacture, but much harder to replicate.
Try to work out a circuit diagram to see what it does, and how that could be replicated.
Thanks for the response.
According to the datasheet, it’s a Flash ROM.
https://pdf1.alldatasheet.com/datasheet-pdf/view/61764/FUJITSU/MB90F553A.html
Some user on reddit was kind enough to look into it and they suggested a DIY parallel programmer can be used to read/write to it.
Or they suggested the below programmer which was originally used to program these chips in circuit.
I’m still reading more on the topic and trying to figure out if this is something within my capabilities. Otherwise I’ll have to find someone experienced who I can send the board to. Good thing about the monitor is the board where the chip sits in is nice and tiny.
This would be my approach as well. Assuming the chip doesn’t do too much in a CRT. Just a guess.
Tbh… As the majority of things are analogue, you might find that it’s only job is to run the i2c bus to control other chips.
The bus Pirate could look at the i2c bus to see what’s being sent.
Try reading the signals a few times to see what changes… Does it have digital controls? That might be it’s function…
If it is, then it should be a simple task to replicate those functions.
If it uses the adc then it might be a bit harder, but I’d guess it just adjusts a few i2c pots… It would be the simplest solution which most manufacturers take