42.6.1.4 Operating Modes

SLCD supports up to eight COM and up to three bias voltages. The multiplexing and bias configurations are set independently by writing to the Duty Ratio bits and to the Bias Setting bits in Control A register (CTRLA.DUTY and CTRLA.BIAS, respectively). CTRLA.DUTY defines the number of COM lines used (NB_COM), as shown in the table below, and thus the number of phases.

Table 42-1. Duty Selection (CTRLA.DUTY)
DUTY[2:0]	Duty (NB_COM)	Recommended Bias	COM Pins
0x0	1	Static	COM0
0x1	2	1/2	COM0..1
0x2	3	1/3	COM0..2
0x3	4	1/3	COM0..3
0x4	6	1/3	COM0..5
0x5	8	1/4	COM0..7

The CTRLA.BIAS[1:0] bit field defines the number of bias voltage:

Table 42-2. Bias Selection (CTRLA.BIAS)
BIAS[1:0]	Description
00	Static
01	1/2
10	1/3
11	1/4

The LCD controller will drive different waveforms according to the different bias configurations. The LCD controller supports two types of driving waveform, bit-inversion (type A, standard) or frame-inversion (type B, low-power). The frame-inversion mode has a lower switching frequency than the bit-inversion mode, and thus reduced power consumption comparing to standard waveform. Both waveform modes have the same period, and their DC-component is null.

By default the low-power waveforms mode is enabled. To select frame-inversion mode, write a zero in the Waveform Mode bit in Control A register (CTRLA.WMOD). To select bit-inversion mode, write a '1' to CTRLA.WMOD.

The following section illustrates how the SLCD controller drives different LCD panels.

For static bias, standard and low-power waveform are identical. However, for 1/2, 1/3 and 1/4 bias, low-power waveform provides a lower toggle rate comparing to the standard waveform.

Figure 42-4. Static Bias Waveform template

Figure 42-5. Static Bias and Duty Waveform

Figure 42-7. 1/2 bias, 1/2 Duty Standard Waveform

The low-power waveform template can be derived from the standard one by separating the standard waveform template into two subframe templates, as shown in the following figure:

Figure 42-8. Derive Low-Power Waveform Template from Standard Waveform Template

Figure 42-9. 1/2 Bias, 1/2 Duty Low-Power Waveform

Figure 42-10. 1/3 Bias Standard Driving Waveform Template and Combination

Figure 42-11. 1/3 Bias, 1/4 Duty, Standard Waveform

Figure 42-12. 1/3 Bias, 1/4 Duty, Low-Power Waveform

Figure 42-13. 1/4 Bias Standard Driving Waveform Template and Combination

Figure 42-14. 1/4 Bias, 1/8 Duty, Standard Waveform

Figure 42-15. 1/4 Bias, 1/8 Duty, Low-Power Waveform