AT89LP6440 datasheet(75/194 Pages) ATMEL

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3706A–MICRO–9/09

AT89LP6440 - Preliminary

13.3.1.1

Normal Mode

The simplest waveform mode is when CP/RL2 =0 and T2CM1-0 = 01B. In this mode the fre-

quency of the output is determined by the TOP value stored in RCAP2L and RCAP2H and

output edges occur at fractions of the timer period. Figure 13-4 shows an example of outputting

two waveforms of the same frequency but different phase by using the toggle on match action.

More complex waveforms are achieved by changing the TOP value and the compare values

more frequently.

Figure 13-4. Normal Mode Waveform Example

13.3.1.2

Clear-Timer-on-Compare Mode

Clear-Timer-on-Compare (CTC) mode occurs when the CTCx bit of a compare channel is set to

one. CTC Mode works best when Timer 2 is in capture mode (CP/RL2 =1) to allow the full range

of compare values. In CTC Mode the compare value defines the interval between output events

because the timer is cleared after every compare match. Figure 13-5 shows an example wave-

form using the toggle on match action in CTC Mode.

Figure 13-5. CTC Mode Waveform Example

13.3.1.3

Dual-Slope Mode

The dual-slope mode occurs when CP/RL2 =0 and T2CM

1-0 = 1xB. In this mode the frequency

of the output is determined by the TOP value stored in RCAP2L and RCAP2H and output edges

occur at fractions of the timer period on both the up and down count. Figure 13-6 shows an

example of outputting two symmetrical waveforms using the toggle on match action. More com-

plex waveforms are achieved by changing the TOP value and the compare values more

frequently.

{RCAP2H,RCA2L}

CP/RL2 = 0, T2CM1-0 = 01B, DCEN = 0

CCA

{CCAH,CCAL}

{CCBH,CCBL}

CCB

CP/RL2 = 1

CCA

{CCAH,CCAL}

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