I need to know how to use the D+ and D- pins for USB communication on the Atmel ATC51 series :mu:Cs, specifically wrt opcode (datasheet and user manual don't have much). If anyone has any useful links/info on this, I'd really appreciate it if you could post it here. Thanks.
the d+ and d- are used for differential data transmission (or whatever it is called in english, sory, not native). The meaning of that is that when d+ is high, d- is low and vice versa. Also, there are standards for cross-points of the signals, etc. You can find it @ www.usb.org the document, which you need is called "ellectrical characteristics" and considered to be the most borring piece of text to read.
I don't think 8051 can do it, specially not one like the AT89C51, because the processor throughput wont be enough... the nearest alternative would be an AVR like the ATMEGA16
depending on what else you need to do with the 8051, the TI CC1111 has USB, single cycle instructions and a 3 ISM band transciever for around US$4.50. You just can't buy them at the moment as they seem to be very popular.