IOWR and direct adress access

>When you use "direct access" you end up using stx/ldx instructions. When you use

the IOWR/IORD macros, you get the stxio/ldxio instructions. The "io" instructions

bypass the data cache.

thanks,Now i understand it , when a do the memory transfer, maybe it first move to data cache, not move to the address i what.

>Do you mean you didn't see any data on your terminal? ... or nothing was

transmitted at all? Your terminal software simply may not be displaying NULL

Yes, nothing was transmitted, I made the terminal program in PC and it can display any data when received. I set the display mode in hex mode.