P89X51RB2HBA will not program

[clim]

Hi All,

I am trying to program the P89C51RB2HBA with the Flash Magic but encounter the

[erik malund]

You are using RC reset are you not?

Erik

[Andy Ayre]

Being able to program some devices but not others while using the same PC, settings and target hardware, sounds like an electrical problem.

Have you checked for glitches or ripple on VCC, GND, XTAL pins? What are the voltages on EA, PSEN, P2.6 and P2.7? Are they all within the ranges allowed for logic 0 or 1 as required by the datasheet for ISP entry?
As Erik asked - are you using an RC reset or a supervisor?

[clim]

Erik and Andrew,

Thanks for your speedy reply.  My reset circuit is same as the one in the Philips AN461 figure 3.  

I also did some measurement as you suggested and here are the finding:
The ripple on the VCC, GND and XTAL is not more then 140mV.
The voltage on the EA pin = 5V, PSEN = 40mV, P2.6  and P2.7 = 4.92V.

Thanks again.
Clarence

[Andy Ayre]

I don't know for sure, but perhaps the 140mV ripple is causing the problem?

[clim]

Andrew,

I had brought down my VCC ripple from 140mV to 72mV p-p with bypass cap.  Micro controller still won't program.

Clarence

[Andy Ayre]

What reset circuit/device are you using? I know that some people have reported better reliability in the past when using a reset supervisor device.

[erik malund]

There is a pargagrph in the errata for this device which basically stets "if you use RC reset you are screwed'

Erik

[clim]

My reset circuit is RC design same as the one in Philips AN461 page 12.  I am open for a reset supervisor device.  Any suggestion?

Thanks
Clarence

[erik malund]

MAX810, oddly enough you need get it not from Maxim, but from Philips.  If you are prototyping Maxim will probably give you smaples, but production quantities are hard to get.

Erik

[clim]

Thanks Erik!