168
8025I–AVR–02/09
ATmega48P/88P/168P/328P
When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is overridden
according to
. For more details on automatic port overrides, refer to
”Alternate Port Functions” on page 80
Note:
See
”Alternate Functions of Port B” on page 82
for a detailed description of how to define the
direction of the user defined SPI pins.
The following code examples show how to initialize the SPI as a Master and how to perform a
simple transmission. DDR_SPI in the examples must be replaced by the actual Data Direction
Register controlling the SPI pins. DD_MOSI, DD_MISO and DD_SCK must be replaced by the
actual data direction bits for these pins. E.g. if MOSI is placed on pin PB5, replace DD_MOSI
with DDB5 and DDR_SPI with DDRB.
Table 16-1.
SPI Pin Overrides
Pin
Direction, Master SPI
Direction, Slave SPI
MOSI
User Defined
Input
MISO
Input
User Defined
SCK
User Defined
Input
SS
User Defined
Input