Introduction - Freescale Semiconductor MCF54455 Reference Manual

Chapter 30
DMA Timers (DTIM0–DTIM3)
30.1

Introduction

This chapter describes the configuration and operation of the four direct memory access (DMA) timer
modules (DTIM0, DTIM1, DTIM2, and DTIM3). These 32-bit timers provide input capture and reference
compare capabilities with optional signaling of events using interrupts or DMA triggers. Additionally,
programming examples are included.
The designation n appears throughout this section to refer to registers or
signals associated with one of the four identical timer modules: DTIM0,
DTIM1, DTIM2, or DTIM3.
30.1.1 Overview
Each DMA timer module has a separate register set for configuration and control. The timers can be
configured to operate from the internal bus clock (f sys ) or from an external clocking source using the
DTnIN signal. If the internal bus clock is selected, it can be divided by 16 or 1. The selected clock source
is routed to an 8-bit programmable prescaler that clocks the actual DMA timer counter register (DTCNn).
Using the DTMRn, DTXMRn, DTCRn, and DTRRn registers, the DMA timer may be configured to assert
an output signal, generate an interrupt, or request a DMA transfer on a particular event.
The GPIO module must be configured to enable the peripheral function of
the appropriate pins (refer to
prior to configuring the DMA Timers.
Freescale Semiconductor
NOTE
NOTE
Chapter 16, "Pin Multiplexing and Control")
30-1