Unable to access P89CRD2BN after write

[dptxp]

I never had any problem with the old RD2 or with P89C61X2BN, but here I am unable to
access the device by ISP (yes I keep PSEN low at time of reset) once I program the
device, security bit set or not.

No problems with P89C61X2.

[Andy Ayre]

Have you verified the voltage on PSEN and VCC using a scope at the pin itself?

Andy

[dptxp]

NO. I keep psen shorted to ground till about 1 sec after power-up.
Justlike for P89C61X2. The old H version too worked this way.

89CRD2BN can be accessed till programmed. Not after that.

[Andy Ayre]

If you can access it until after being programmed then:
  - serial comms works
  - ISP entry method does not work

So you should check the voltages on PSEN and VCC at the pins themselves. Make sure the signals match the requirements in the datasheet.

Andy