I managed to download a simple program in a P89CRC2BN using Flash magic but now I can
Yes, you need to implement the workaround on the errata sheet (the reset network) if you haven't already. Please refer to the errata sheet for the details.
If you have only programmed the device once, then you haven't yet tested the ISP entry method. Devices are shipped with the status byte set, so they reset into ISP mode.
No way, I followed the instructions in the errata sheet about P89C51Rx2 page 3 i guess, title:
FUNCTIONAL DEVIATIONS OF P89C51RX2 /01
I did the connection as shown in the two circuits. Vpp pin connected to +5 throw a 3,3 K resistor and to ground throw a 10 uF capacitor. And i connected Psen pin to +5v throw a 10 uF capacitor and to ground throw a 3,3 K resistor. The circuit of the the reset pin is the same of the an461 i only used a 4148 diode instead of the one used in the circuit. The cristal is a 12 MHz. In the meantime i "burned" another chip with a program that make the led blinking just to be sure that the circuit is running the program loaded. Should i increase the value of the two 3,3 K resistor to a 33 K as i read somewhere in the forum. May i send you the schematic of the circuit i am using?
Thank you
Francesco Fontana
So you can connect to the device once and program, but you can't do it a second time? Double-check the voltages on the pins required for ISP entry as detailed in the datasheet for the device. Are you selecting 89C51RC2xx in Flash Magic rather than 89C51RC2Hxx?
Also try and work through the Flash Magic application note "what to do when ISP does not work" - it may give me some clues as to what the problem might be.
I found the problem. The psen pin was not joninted with the iron, i found it only with the dvm as you suggested. I am sorry. Thank you very much for your support. I just started yesterday to enjoy my first 8051 based circuit.
Thank you again.
Francesco Fontana