ST7571 datasheet(23/76 Pages) SITRONIX

23 / 76 page

ST7571

Ver 1.5a

23/76

2009/7/21

7.3 LCD DISPLAY CIRCUITS

Oscillator

This is on-chip Oscillator without external resistor. When the internal oscillator is used, this pin must connect to VDD1; when

the external oscillator is used, this pin could be input pin. This oscillator signal is used in the voltage converter and display

timing generation circuit.

Display Timing Generator Circuit

This circuit generates some signals to be used for displaying LCD. The display clock, CL (internal), generated by oscillation

clock, generates the clock for the line counter and the signal for the display data latch. The line address of on-chip RAM is

generated in synchronization with the display clock and the display data latch circuit latches the 128-bit display data in

synchronization with the display clock. The display data, which is read to the LCD driver, is completely independent of the

access to the display data RAM from the microprocessor. The display clock generates an LCD AC signal (FR) which

enables the LCD driver to make an AC drive waveform, and also generates an internal common timing signal and start

signal to the common driver. The frame signal or the line signal changes the M by setting internal instruction. Driving

waveform and internal timing signal are shown in Fig. 13.

FR(Internal)

Frame

COM0

COM10

SEGn

CL(Internal)

127

10 11

128

127

126

125

124

123

122

121

120

Fig. 13

Frame AC Driving Waveform (Duty Ratio: 1/129)

Fig. 14

N-Line Inversion Driving Waveform (N=5,Duty Ratio=1/129)

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