Hi Jacek,

A quick read of the 89S8252 data sheet says you can use both uart and spi at the same time, although it they share an interrupt vector. Basically an extension of the current uart interrupt, where in the ISR you must test RI and TI to see who caused it, here you also have to test SPIF also.

It would appear that the SPI has a double interrupt enable, not only do you have to set ES as well as SPIE to enable the SPI interrupt.

It looks like it should be fairly easy to use, simpler than the bit-banging SPI I've implemented before.

Good luck with it.

Dennis