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If I understand you correctly, you have a computer without a parallel port an want to make your own parallel port using 8051.

First, from the link, it appears that the 8051 clone mentioned there is driving the port directly using the shown circuit.

So I don't see why you'd need a cable with both parallel port and RS-232. If you want to avoid using 8051, you could just buy a USB to parallel cable.

Also, I'd recommend that you use a USB to RS-232 chip directly instead of using a USB to RS-232 cable. The main benefit of such setup is that the chip should negotiate enough current for you to be able to power the circuit directly from USB port. You may be able to make a circuit which would support a USB to RS-232 chip directly or you could buy one prefabricated.