17.6Compare Match Output Unit ................................................................................145
17.7Modes of Operation .............................................................................................146
17.8Timer/Counter Timing Diagrams .........................................................................150
17.9Asynchronous Operation of Timer/Counter2 .......................................................152
17.10Timer/Counter Prescaler ...................................................................................153
17.11Register Description ..........................................................................................154
18 SPI – Serial Peripheral Interface ......................................................... 162
18.1Features ..............................................................................................................162
18.2Overview ..............................................................................................................162
18.3SS Pin Functionality ............................................................................................167
18.4Data Modes .........................................................................................................167
18.5Register Description ............................................................................................169
19 USART0 ................................................................................................. 172
19.1Features ..............................................................................................................172
19.2Overview ..............................................................................................................172
19.3Clock Generation .................................................................................................173
19.4Frame Formats ....................................................................................................176
19.5USART Initialization .............................................................................................178
19.6Data Transmission – The USART Transmitter ....................................................180
19.7Data Reception – The USART Receiver .............................................................182
19.8Asynchronous Data Reception ............................................................................186
19.9Multi-processor Communication Mode ................................................................189
19.10Register Description ..........................................................................................191
19.11Examples of Baud Rate Setting .........................................................................195
20 USART in SPI Mode ............................................................................. 200
20.1Features ..............................................................................................................200
20.2Overview ..............................................................................................................200
20.3Clock Generation .................................................................................................200
20.4SPI Data Modes and Timing ................................................................................201
20.5Frame Formats ....................................................................................................201
20.6Data Transfer .......................................................................................................204
20.7AVR USART MSPIM vs. AVR SPI ......................................................................206
20.8Register Description ............................................................................................207
21 2-wire Serial Interface .......................................................................... 210
21.1Features ..............................................................................................................210
iv
ATmega48/88/168
2545M–AVR–09/07
ATMEL [ ATMEL ]
