How to restore the bootloader of a AT89C51RD2?

several years ago, the manufacturers stopped publishing parallel programming info because their support was overloaded by requests from "kitchen table programmer makers" and I have anecdotal evidence that a major issue was that the chips were, in one or more instances, not programmed 'fully' i.e. they lost the programming after a while and, of course, the complaint was "your chip" not "my 'programmer'

my recommendation is throw away the $2 chip, instead of spending a lot of time and money trying to recover it.

Erik

several years ago, the manufacturers stopped publishing parallel programming info because their support was overloaded by requests from "kitchen table programmer makers" and I have anecdotal evidence that a major issue was that the chips were, in one or more instances, not programmed 'fully' i.e. they lost the programming after a while and, of course, the complaint was "your chip" not "my 'programmer'

my recommendation is throw away the $2 chip, instead of spending a lot of time and money trying to recover it.

Erik

Erik, that explains a lot. Now I understand why older datasheets are so detailed in this area, and the current ones don't even touch the subject.

And that also explains why projects like Willem and others are abandoned since 2005 or so.

Thanks anyway. I think you're right about throwing away the chips, but I have 22 units of them, that hurts!

Eduardo

find someone with a programmer if RC2 works (or the 'youngest version of an Atmel chip'), great, if not you have lost the chip anyway

Good idea, Erik! If nothing else works, I'll certainly do that.

However, following your last post, I went after some older datasheets, the ones that still bring information on parallel programming, and see this info I found on AT89C51RC, quite interesting:

"Chip Erase Sequence: Before the AT89C51RC can be reprogrammed, a Chip Erase operation
needs to be performed. To erase the contents of the AT89C51RC, follow this sequence:
1. Raise VCC to 6.5V.
2. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
3. Power VCC down and up to 6.5V.
4. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
5. Power VCC down and up."

This is quite easy to implement. And it may work, according to the AT89C51RD2 datasheet:

"Only a full chip erase in parallel mode (using a programmer) or ISP command can reset the soft-
ware security bits."

So, it seems all I need to do is to build a simple circuit to feed 6.5V to Vcc thru a transistor, and write some simple code for a working MCU to signal the transistor and ALE at the correct timings.

Since this won't take a long time to implement, I'll give it a shot. What do you think about this possible solution?

Thanks for the help!

Eduardo

That's what eBay, or such, are good for, you can find someone who already has a programmer, but needs devices for some legacy product/project.

The other reason build-your-own prom programmers disappeared is the cheapness of reasonably professional alternatives, and the fact the market for antiquated devices keeps shrinking.

Indeed, eBay is a good way to end this history if all else fails. Anyone interested can have all my 22 chips for $30.00 plus shipping.

I'm now waiting for a reply from Atmel's support. This is my last try. I want to confirm the correct procedure for a complete AT89C51RD2 erase. I can't find any document on the subject for this specific chip.