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RM0351 Liquid crystal display controller (LCD)
690
Blink
The segment driver also implements a programmable blink feature to allow some pixels to
continuously switch on at a specific frequency. The blink mode can be configured by the
BLINK[1:0] bits in the LCD_FCR register, making possible to blink up to 1, 2, 4, 8 or all
pixels (see Section 22.6.2: LCD frame control register (LCD_FCR)). The blink frequency
can be selected from eight different values using the BLINKF[2:0] bits in the LCD_FCR
register.
Table 129 gives examples of different blink frequencies (as a function of ck_div frequency).
22.3.5 Voltage generator and contrast control
LCD supply source
The LCD power supply source may come from either the internal step-up converter or from
an external voltage applied on the VLCD pin. Internal or external voltage source can be
selected using the VSEL bit in the LCD_CR register. In case of external source selected, the
internal boost circuit (step-up converter) is disabled to reduce power consumption.
When the step-up converter is selected as V
LCD
source, the V
LCD
value can be chosen
among a wide set of values from V
LCDmin
to V
LCDmax
by means of CC[2:0] (Contrast
Control) bits inside LCD_FCR (see Section 22.6.2) register. New values of V
LCD
takes effect
every beginning of a new frame.
When external power source is selected as V
LCD
source, the V
LCD
voltage must be chosen
in the range of V
LCDmin
to V
LCDmax
(see datasheets). The contrast can then be controlled by
programming a dead time between frames (see Deadtime on page 672).
A specific software sequence must be performed to configure the LCD depending on the
LCD power supply source to be used. Here we consider the LCD controller is disabled prior
to the configuration sequence.
Table 129. Blink frequency
BLINKF[2:0]
bits
ck_div frequency (with LCDCLK
frequency of 32.768 kHz)
32 Hz 64 Hz 128 Hz 256 Hz
0 0 0 4.0 Hz N/A N/A N/A
0 0 1 2.0 Hz 4.0 Hz N/A N/A
0 1 0 1.0 Hz 2.0 Hz 4.0 Hz N/A
0 1 1 0.5Hz 1.0Hz 2.0Hz 4.0Hz
1 0 0 0.25 Hz 0.5 Hz 1.0 Hz 2.0 Hz
1 0 1 N/A 0.25 Hz 0.5 Hz 1.0 Hz
1 1 0 N/A N/A 0.25 Hz 0.5 Hz
1 1 1 N/A N/A N/A 0.25 Hz
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