P89C51RD2BN ISP problem!

[kiransm]

Hi all,
I am new to this list.
I am using P89C51RD2BN, through ISP i am trying to program it. but it is not entering into ISP mode.  I am using FlashMagic to do programming. it is giving me error as "Unable to connect at specified boud rate. Try reducing the boud rate"!
I have made circuitry as per AN461, the only difference is that in the reset circuit i am using 8.2K resister instead of 10K specified in AN461. also EA/VPP line is kept floating but in AN461 they have shown that that pin is connected to ground through 0.1uF capacitor. is the problem i am facing is due to these differences?. I have a jumper for PSEN pin to put microcontroller in to ISP.
please help me.

looking for your reply!

thanking in advance,

regards,
Kiran

[Jan Waclawek]

Have a better look at VPP/EA in schematics in AN461 - it is not just connected to GND via a capacitor - it IS connected to VCC (so the capacitor is only for decoupling).

Jan Waclawek

[kiransm]

aah!! ok ok!
actualy i got confused because in the same document (AN461) on page 12 they have given a schematic for typical ISP circuit, in that VPP is grounded through cap without connecting to the Vcc. i guess that is for c51RD+ microcontrollers!

thanks for fast reply

regards,
Kiran

[Andy Ayre]

Reset supervisor ICs are recommended for flash based microcontrollers. You might want to consider using one of those.

[erikm]

Reset supervisor ICs are recommended for flash based microcontrollers

I disagree!

Reset supervisor ICs are MANDATORY for flash based microcontrollers.

[kiransm]

Thanks everybody!!
my problem has been solved! actually it was the issue of VPP pin.
i have not connected it to VCC, insted of connecting it to VCC it was connected to GROUD on the PCB and also bootloader of my P89C51RD2 was get erased by mistake!!

Thanks again!

regards,
Kiran