Introduction - Freescale Semiconductor MCF54455 Reference Manual

Chapter 29
Programmable Interrupt Timers (PIT0–PIT3)
29.1

Introduction

This chapter describes the operation of the four programmable interrupt timer modules: PIT0–PIT3.
29.1.1 Overview
Each PIT is a 16-bit timer that provides precise interrupts at regular intervals with minimal processor
intervention. The timer can count down from the value written in the modulus register or it can be a
free-running down-counter.
29.1.2 Block Diagram
Internal Bus
Prescaler
Clock (f )
sys/2
PRE[3:0]
29.1.3 Low-Power Mode Operation
This subsection describes the operation of the PIT modules in low-power modes and debug mode of
operation. Low-power modes are described in the power management module,
Management." Table 29-1
each mode.
Freescale Semiconductor
Internal Bus
16-bit PCNTRn
16-bit PIT Counter
EN
OVW
DOZE
16-bit PMRn
DBG
Internal Bus
Figure 29-1. PIT Block Diagram
shows the PIT module operation in low-power modes and how it can exit from
COUNT = 0
PIF
Load
Counter
PIE
RLD
Chapter 9, "Power
To Interrupt
Controller
29-1