ATAM894 datasheet(49/97 Pages) ATMEL

49 / 97 page

4679D–4BMCU–05/05

ATAM894

Most of the timer modes use their compare registers alternately. After the start has been acti-

vated, the first comparison is carried out via the compare register 1, the second is carried out via

the compare register 2, the third is carried out again via the compare register 1 and so on. This

makes it easy to generate signals with constant periods and variable duty cycle or to generate

signals with variable pulse and space widths.

If single-action mode is set for one compare register, the comparison is always carried out after

the first cycle via the other compare register.

The counter can be started and stopped via the control register T3C. This register also controls

the initial level of the output before start. T3C contains the interrupt mask for a T3I input

interrupt.

Via the Timer 3 clock-select register, the internal or external clock source can be selected. This

generate also an interrupt if the T3EIM bit is set and the Timer 3 is stopped (T3R = 0) in the T3C

The status of the timer as well as the occurrence of a compare match or an edge detect of the

input signal is indicated by the status register T2ST. This allows identification of the interrupt

source because all these events share only one timer interrupt.

Timer 3 compares data values.

The Timer 3 has two 8-bit compare registers (T3CO1, T3CO2). The compare data value can be

‘m’ for each of the Timer 3 compare registers.

The compare data value for the compare registers is: m = x +1

≤x ≤255

Timer 3 – Mode 1: Timer/Counter

The selected clock from an internal or external source increments the 8-bit counter. In this mode,

the timer can be used as event counter for external clocks at T3I or as timer for generating inter-

rupts and pulses at T3O. The counter value can be read by the software via the capture register.

Figure 6-26.

Counter Reset with Each Compare Match

0012

T3R

Counter 3

CM31

INT5

T3O

CM32

ATAM894 Datasheet(PDF) 49 Page - ATMEL Corporation