Davide Gironi writes:
Driving that IC is pretty simple, expecially if you have a dedicated SPI hardware interface, like many microchip has.
The ATmega8, used in this example has a dedicated SPI Control Register (SPSR) that one can use to setup the SPI interface.
This library can drive more then one MCP49XX of the same series at the same time, this is done just by selecting the chip using a SS channel for each one.
See the full post on his blog.
Check out the video after the break.