I am facing a very strange problem in ISP programming of P89c51RD2 using flash magic. I am not able establish the communication between flash magic PC and my hardware.
First I will describe my hardware.

I provided a jumper link on PSEN pin so that I can connect PSEN to ground through 2K2 resistor during power on. Insertion of this link will take controller in ISP mode.

EA/VPP pin is connected to VCC.

For RS232 communication I am not using any handshake signals.

After power on with the above mentioned link in place I expect that the controller will start in ISP mode and then the communication should start. This is not happening.

First I had a doubt on RS232 hardware. In order to make sure that the hardware is working fine I removed the controller from the socket and shorted RXD and TXD pins of socket together. When I type something in hyper terminal I am getting the character back. This means that the character transmitted by PC is converted to TTL level by MAX232 chip and that character is received on RXD pin. This RXD pin is shorted to TXD pin of socket so the same character is transmitted back to PC and that character is visible in hyper terminal window. So my hardware is working perfectly all right.

After that I removed the link between RXD and TXD and inserted controller back into socket. This after booting controller in ISP mode I checked whether it functions in loopback mode by typing "U" using hyper terminal. I did not get any loopback.

I suspect that the controller is not booting in ISP mode at all and hence I am not getting the loopback.

After that I shorted PSEN to ground and reseted the controller again. Still this time also I could not get the loopback.

This is a very wierd problem and I am not able to locate the exact reason. I used this same analogy in the hardware and never faced this kind of problem.

Have anybody faced this kind of problem? Can somebody guide me for this?

Regards!
Girish R. Ghanekar