DMA Timer Programming Model

System Clock (÷1 or ÷16)

DTINn

DTOUTn

IRQn

DREQn

 

 

 

 

 

15

 

 

 

 

 

 

0 7

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DMA Timer

 

 

DMA Timer Mode Register (DTMRn)

 

 

DMA Timer Extended Mode

 

 

 

 

 

 

 

 

Prescaler

 

 

 

 

Mode Bits

 

 

Register (DTXMRn)

 

 

 

 

Clock

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Generator

 

 

 

 

Divider

 

 

 

 

 

 

 

 

 

 

 

 

clock

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Capture

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Detection

 

 

DMA Timer Counter Register (DTCNn)

 

 

 

 

 

 

 

 

 

(contains incrementing value)

 

 

 

 

31

 

 

 

 

 

 

 

0

 

31

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DMA Timer Capture Register (DTCRn)

 

 

 

DMA Timer Reference Register (DTRRn)

 

(latches DTCN value when triggered by DTINn)

 

 

 

(reference value for comparison with DTCN)

 

 

 

 

7

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DMA Timer Event Register (DTERn) (indicates capture or when DTCN = DTRRn)

Figure 21-1. DMA Timer Block Diagram

21.1.1 Key Features

Each DMA timer module has the following features:

Maximum timeout period of 266,521 seconds at 66 MHz (~74 hours)

15-ns resolution at 66 MHz

Programmable sources for the clock input, including external clock

Programmable prescaler

Input-capture capability with programmable trigger edge on input pin

Programmable mode for the output pin on reference compare

Free run and restart modes

Programmable interrupt or DMA request on input capture or reference-compare

21.2 DMA Timer Programming Model

The following features are programmable through the timer registers, shown in Table 21-1:

21.2.1 Prescaler

The prescaler clock input is selected from system clock (divided by 1 or 16) or from the corresponding timer input, DTINn. DTINn is synchronized to the system clock. The synchronization delay is between two and three system clocks. The corresponding

21-2

MCF5282 User’s Manual

MOTOROLA

Page 448
Image 448
Motorola MCF5282, MCF5281 user manual DMA Timer Programming Model, Key Features, Prescaler