Hi there !!!
Im trying to programm an external microcontroller ussing arduino uno iscp but im stuck at the middle i dont know how to do it please a little help with be great 
i connect arduino to the pc and i upload the isp scatch to arduino.... i want to use arduino as a bridge for uploading hex files to the IC i use keil uvison 4 to make the hex file and the 8051 spi programmer to upload the hex but no success... i want to blink a led at pin 15 (P1.3) of the ic or whatever
The 89C2051 is an entirely different microcontroller family than the AVRs used by most Arduinos. I don't know why you would expect "arduino uno iscp" [sic] to be useful at all, or why you think that the arduino forums have any expertise in doing anything with 2051s...
i use ... the 8051 spi programmer to upload the hex
Wait? What 8051 spi programmer are you talking about?
I've heard that 2051 ISP programming is quite similar to AVR ISP programming "except for the polarity of the reset signal", and that MAY have been added to the ArduinoISP sketch "recently." Are you using ArduinoISP from an up-to-date version of the IDE?
I've heard that 2051 ISP programming is quite similar to AVR ISP programming "except for the polarity of the reset signal", and that MAY have been added to the ArduinoISP sketch "recently.
89C2051 programming is not possible with an Uno ISP. This is due to the 89C family requiring a positive 12 volt pulse during programming, which the Uno is incapable of generating.
The cheapest and easiest way, by far, to program a '2051 is to buy yourself a programmer on eBay. Do a search for "SP200 programmer". They can be had for less than $10, the only catch is the wait for it arrive... from China.
If you need it this week and/or you're spending OPM (other people's money), grab a Atmel Dragon from Digi-key or Mouser or Farnell or... Oh, you'll probably want a zip socket for the Dragon which will cost you way more for the socket alone from Digi-key than the entire programmer from China.
Edit: One downside to the Dragon is that you'll need Atmel Studio installed in order to use it.
Thnx alot for the help 