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2014-07-02 - Tiny Gecko Family - d0034_Rev1.20
508
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• LFCLK16: LFACLK
LCDpre
= LFACLK/16
• LFCLK32: LFACLK
LCDpre
= LFACLK/32
• LFCLK64: LFACLK
LCDpre
= LFACLK/64
• LFCLK128: LFACLK
LCDpre
= LFACLK/128
In addition to selecting the correct prescaling, the clock source can be selected in the CMU.
To use this module, the LE interface clock must be enabled in CMU_HFCORECLKEN0, in addition to
the module clock.
29.3.7.2 Frame rate Division Register
The frame rate is set in the CMU by programming the frame rate division bits FDIV in CMU_LCDCTRL.
This setting should not be changed while the LCD driver is running. The equation for calculating the
resulting frame rate is given from Equation 29.1 (p. 508)
LCD Frame rate Calculation
LFACLK
LCD
= LFACLK
LCDpre
/(1 + FDIV)
(29.1)
Table 29.9. LCD Frame rate Conversion Table
Resulting Frame rate, CLK
FRAME
(Hz)
LFACLK
LCDpre
= 2
kHz
LFACLK
LCDpre
= 1
kHz
LFACLK
LCDpre
=
0.5 kHz
LFACLK
LCDpre
=
0.25 kHz
MUX Mode
Frame- rate
formula
Min
Max
Min
Max
Min
Max
Min
Max
Static
LFACLK
LCD
/2
128
1024
64
512
32
256
16
128
Duplex
LFACLK
LCD
/4
64
512
32
256
16
128
8
64
Triplex
LFACLK
LCD
/6
43
341
21
171
11
85
5
43
Quadruplex
LFACLK
LCD
/8
32
256
16
128
8
64
4
32
Sextaplex
LFACLK
LCD
/12
21.33
170.67
10.67
85.33
5.33
42.67
2.67
21.33
Octaplex
LFACLK
LCD
/16
16
128
8
64
4
32
2
16
Table settings: Min: FDIV = 7, Max: FDIV = 0
29.3.8 Data Update
The LCD Driver logic that controls the output waveforms is clocked on LFACLK
LCDpre
. The LCD data and
Control Registers are clocked on the HFCORECLK. To avoid metastability and unpredictable behavior,
the data in the Segment Data (SEGDn) registers must be synchronized to the LCD driver logic. Also,
it is important that data is updated at the beginning of an LCD frame since the segment waveform
depends on the segment data and a change in the middle of a frame may lead to a DC-component in that
frame. The LCD driver has dedicated functionality to synchronize data transfer to the LCD frames. The
synchronization logic is applied to all data that need to be updated at the beginning of the LCD frames:
• LCD_SEGDn
• LCD_AREGA
• LCD_AREGB
• LCD_BACTRL
The different methods to update data are controlled by the UDCTRL bits in LCD_CTRL.
Summary of Contents for EFM32TG
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