Data Sheet

iv
8161D–AVR–10/09
ATmega48PA/88PA/168PA/328P
17 8-bit Timer/Counter2 with PWM and Asynchronous Operation ...... 144
17.1Features ..............................................................................................................144
17.2Overview .............................................................................................................144
17.3Timer/Counter Clock Sources .............................................................................145
17.4Counter Unit ........................................................................................................145
17.5Output Compare Unit ..........................................................................................146
17.6Compare Match Output Unit ................................................................................148
17.7Modes of Operation .............................................................................................149
17.8Timer/Counter Timing Diagrams .........................................................................153
17.9Asynchronous Operation of Timer/Counter2 .......................................................155
17.10Timer/Counter Prescaler ...................................................................................156
17.11Register Description ..........................................................................................158
18 SPI – Serial Peripheral Interface ......................................................... 166
18.1Features ..............................................................................................................166
18.2Overview .............................................................................................................166
18.3SS
Pin Functionality ............................................................................................171
18.4Data Modes .........................................................................................................171
18.5Register Description ............................................................................................173
19 USART0 ................................................................................................. 176
19.1Features ..............................................................................................................176
19.2Overview .............................................................................................................176
19.3Clock Generation .................................................................................................177
19.4Frame Formats ....................................................................................................180
19.5USART Initialization ............................................................................................182
19.6Data Transmission – The USART Transmitter ....................................................183
19.7Data Reception – The USART Receiver .............................................................186
19.8Asynchronous Data Reception ............................................................................190
19.9Multi-processor Communication Mode ................................................................193
19.10Register Description ..........................................................................................195
19.11Examples of Baud Rate Setting ........................................................................199
20 USART in SPI Mode ............................................................................. 204
20.1Features ..............................................................................................................204
20.2Overview .............................................................................................................204
20.3Clock Generation .................................................................................................204
20.4SPI Data Modes and Timing ...............................................................................205