AN1048

LCD drive signals

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resistors of equal value, externally connected to the I/O pin. By using an MCU with flexible

I/O pin configuration, a duplexed LCD drive can be implemented with only 2 external

resistors bridge (each on two com lines).

Figure 3.

Basic LCD Segment Connection in duplexed mode

Figure 4.

LCD signals for duplexed mode (used in the ST7 example)

COM1

COM2

S1

S11

S12

S2

S3

COM1

S11=COM1-S1

+Vdd

S12=COM2-S1

S1

+Vdd

+Vdd

COM2

CASE1

CASE2

CASE3

CASE4

+Vdd/2

+Vdd/2

-Vdd

+Vdd

+Vdd/2

-Vdd/2

-Vdd

+Vdd

+Vdd/2

-Vdd/2

SEGMENT1

SEGMENT2

OFF

ON

ON

OFF

OFF

OFF

ON

ON