ST72589BW datasheet(43/158 Pages) STMICROELECTRONICS

номер детали	ST72589BW

подробное описание детали	8-BIT MCU WITH NESTED INTERRUPTS, DOT MATRIX LCD, ADC, TIMERS, PWM-BRM, SPI, SCI, I²C, CAN INTERFACES

PDF	158 Pages

Scroll/Zoom	100%

производитель	STMICROELECTRONICS [STMicroelectronics]

домашняя страница	http://www.st.com

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43 / 158 page

ST72589BW, ST72389BW

43/158

LCD DRIVER (Cont’d)

7.1.3 Segment and Common Output signals

Each dot of the LCD dot matrix panel is turned on

when the differential voltage between the segment

signal and the common signal increases over a

certain threshold, it is turned off when the voltage

is below the threshold voltage. The common sig-

nals determine the select timing within a frame cy-

cle (see Figure 27). The common signals have

similar waveforms to the segments, but different

phases.

Figure 27. Waveforms on LCD Outputs

Each common signal shows a high signal ampli-

tude (VLCD-VSS) only at the corresponding sec-

tion of a frame time. At the other sections of the

frame, the signal amplitude is low (3/4VLCD-1/

4VLCD). A dot can be turned-on only at phases

with high signal amplitude.

In 1/8 duty cycle mode, one frame is divided into 8

sections, and each section is divided into two

phases, phase 0 and 1. In 1/4 duty cycle mode,

the number of sections is reduced to 4. This

means the waveform pattern repeats faster in 1/4

duty cycle mode than 1/8 mode and the average

voltage and the ON/OFF duty cycle on a selected

pin is higher than in 1/8 mode. This results in a bet-

ter contrast of the display.

Note: The LCD must be disabled before entering

HALT mode or ACTIVE HALT mode.

Figure 28. LCD outputs with 1/8 Multiplex

VLCD

3/4

1/2

1/4

GND

01 01

Common selected

VLCD

3/4

1/2

1/4

GND

010 1

Common off

VLCD

3/4

1/2

1/4

GND

0 101

Segment selected

VLCD

3/4

1/2

1/4

GND

01 01

Segment off

VLCD

3/4

1/2

1/4

GND

COM8

VLCD

3/4

1/2

1/4

GND

COM7

VLCD

3/4

1/2

1/4

GND

SEG1

VLCD

3/4

1/2

1/4

GND

SEG2

ONE FRAME PERIOD

COM8

COM7

COM6

COM5

COM4

COM3

COM2

COM1

0 101 0101

01 0101

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