Programming a Beautiful C Packaged 8751(8051) & Problems

[hardwarecop]

Hello everyone,

it's me again in need of some help. It should be pretty easy for experienced since I'm a greenhorn in this field asking questions that might go without saying (I don't know).

So there's my EPROM programmer that gives me a Vpp of 21V and has the ability to program 2716 EPROMs way up to all the new ones. Unfortunately, the C8751-8 I got, which I assume also having 21V Vpp since the other D8751H has it as well is not supported by the programmer. Instead, it only supports programming the internal EPROM of a 87C51 which has 12.5V of Vpp.

The problem now:
My intention is it to write some software to that beautiful C8751's internal EPROM without designing a specific programmer with software (well obviously I'm unable to do this on my own). But after some research I've found a quite interesting page saying that the way the 8751's EPROM is being programmed exactly matches the one of a generic 2732 EPROM (http://www.8051bits.com/misc-projects/misc-8051/misc-8051.html)

So his solution is to build an adapter that makes the 8751 look like a 2732 to the EPROM programmer. Unfortunately I'm stuck at some waveforms that are not very clear to me, seen in the picture I've attached down below. It's not very clear to me why/how the adapter design guy managed to split the "/CE" signal into "/PROG" and "/ENABLE" signal for the 8751? Or is it the same when it comes to programming that particular MCU? It seems like that he's used a M74LS32P to solve this, but I absolutely don't understand how. So also please forgive me if I am neglecting any basic knowledge, actually I don't have much

BTW, also the waveforms of the address bus is different between 2732 and 8751. Could anything unexpected happen when I connect them just straightforward? Is it correct, otherwise to give P2.6 and /PSEN ->GND, /EA -> Vpp, P0/P1/P2.0-2.3 their respective data and address lines and P2.7 and /PROG(ALE) the OR-gates (SOMEHOW)?

http://www.cpu-galaxy.at/cpu/Ram%20Rom%20Eprom/Microcontroller/Intel%208751%20section-Dateien/D8751H.pdf

That's the 8751's datasheet BTW for reference. I'm not doing this for homework or something like this but only for fun having some beautiful C-packaged MCUs controlling things in my room

Is everything clear in my question? Any help would be greatly appreciated. Thank you so much in advance.

Greetings,
Frank

[aberco]

If I remember correctly, yes you can access the EPROM section easily, but the 8751 needs to be clocked with a 8MHz crystal as well.

I have seen DYI programming adapters that piggy back on regular EPROM programmers, but it was a long time ago.

[hardwarecop]

Thanks for your help! Of course I will have to supply the 8751 with an external crystal circuit.

So I could program them just by tying the /PROG and /ENABLE together?

Yes the piggy back ones sound really interesting but hard to find.

[aberco]

I would have to dig in my large pile of old electronic magazines. I have seen a few 8051 programmer projects.

[aberco]

You are lucky, I found it!
Electronique Radio Plans, numéro 523 Juin 1991: Adaptateur de programmation pour 8751.

In french, but simple PCB and schematics.

It transform the 8751 or 8753 into a classic 2764 (for 8751 you can only access the lower half of the memory space). There's also a switch to program the protection bit.

Let me scan that for you.
Send me your email or skype by PM