
4551 Group User’s Manual
ii
2.1 I/O pins .................................................................................................................................... 2-2
 2.1.1 I/O ports .......................................................................................................................... 2-2
 2.1.2 Related registers ............................................................................................................ 2-4
 2.1.4 Notes on use .................................................................................................................. 2-8
 2.2 Interrupts ................................................................................................................................. 2-9
 2.2.1 Interrupt functions .......................................................................................................... 2-9
 2.2.2 Related registers .......................................................................................................... 2-10
 2.2.4 Notes on use ................................................................................................................ 2-16
 2.3 Timers .................................................................................................................................... 2-17
 2.3.2 Related registers .......................................................................................................... 2-17
 2.3.4 Notes on use ................................................................................................................ 2-24
 2.4.2 Related registers .......................................................................................................... 2-26
 2.4.4 Notes on use ................................................................................................................ 2-32
 2.5.2 Related registers .......................................................................................................... 2-34
 2.5.4 Notes on use ................................................................................................................ 2-38
 2.6 Power down function .......................................................................................................... 2-39
 2.6.2 Power down function ................................................................................................... 2-41
 2.6.3 Related register ............................................................................................................ 2-44
 2.6.5 Notes on use ................................................................................................................ 2-45
 2.8 Oscillation circuit ................................................................................................................ 2-50
 2.8.1 Oscillation circuit .......................................................................................................... 2-50
 2.8.3 Notes on use ................................................................................................................ 2-51
 Table of contents