AT89LP6440 datasheet(79/194 Pages) ATMEL

79 / 194 page

3706A–MICRO–9/09

AT89LP6440 - Preliminary

Figure 13-10. Phase and Frequency Correct Symmetrical (Center-Aligned) PWM

Figure 13-11. Phase Correct Symmetrical (Center-Aligned) PWM

13.4.3

Multi-Phasic PWM

The PWM channels may be configured to provide multi-phasic alternating outputs by the PHS

2-0

bits in T2MOD. The AT89LP6440 provides 1 out of 2, 1 out of 3, 1 out of 4 and 2 out of 4 phase

modes (See Table 13-6). In Multi-phasic mode the PWM outputs on CCA, CCB, CCC and CCD

are connected to a one-hot shift register that selectively enables and disables the outputs (See

Figure 13-12). Compare points on disabled channels are blocked from toggling the output as if

the compare value was set equal to TOP. The PHSD bit in T2MOD controls the direction of the

shift register. Example waveforms are shown in Figure 13-14 on page 81. In order to use multi-

phasic PWM, the associated channels must be configured for PWM operation. Non-PWM chan-

nels are not affected by multi-phasic operation. However, their locations in the shift register are

maintained such that some periods in the PWM outputs may not have any pulses as shown in

Figure 13-13.

The PHS

2-0 bits may only be modified when the timer is not operational (TR2 = 0). Updates to

PHSD are allowed at any time. Note that channels C and D in 1:2 phase mode and channel D in

1:3 phase mode operate normally.

{RCAP2H,RCA2L}

CP/RL2 = 0, T2CM1-0 = 10B, DCEN = 0

Inverted

{CCxH,CCxL}

Non-Inverted

CCx

Duty Cycle Updated

{RCAP2H,RCA2L}

CP/RL2 = 0, T2CM1-0 = 11B, DCEN = 0

Inverted

{CCxH,CCxL}

Non-Inverted

CCx

Duty Cycle Updated

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