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I have read this document:
AN658 - LCD Fundamentals and the LCD Driver Module of 8-Bit PIC® Microcontrollers

I understand that the main concern is to maintain 0 Vdc bias on every pixel when driving LCD display.

But I do not understand why there are multiple bias voltages required to drive backplanes (= common nodes).

Why are required such crazy unintuitive waveforms? enter image description here

Why I can't use just static biasing?
For example when I want to make 1 pixel on:
1st frame would be BP0=1 (common), SEG0=0, the 2nd frame would be BP0=0 (common), SEG0=1. This would make 0 Vdc bias and the pixel would have the maximal contrast.

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    \$\begingroup\$ A specific difference charge voltage is necessary for a specific LCD video level. Erase charge sequence reduces memory effects. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 22 '17 at 8:15
  • \$\begingroup\$ @TonyStewart.EEsince'75 could you be more explanatory? I don't understand your comment. If specific voltage is required, then why not to use that specific single voltage level (static biasing), instead of 3, 4, or 5 different levels? \$\endgroup\$ – Chupacabras May 22 '17 at 20:13
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    \$\begingroup\$ charge storage in LCD is critically dependent on voltage levels for white and black levels as well as other effects such as polarized viewing angle. Until you understand this, I cannot explain. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 23 '17 at 17:54
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Voltage at particular segment is a difference between voltage on two electrodes, lets call them row and column. There are 4 (four!!) cases:

  • Active segment in active row: |Vactivecol - Vactiverow| = Vmax.
  • Nonactive segment in active row |Vactiverow - Vnotcol| = 1/3 Vmax.
  • Nonactive segment in nonactive row while this segment column electrode is active |Vactivecol - Vnotrov| = 1/3 Vmax.
  • Nonactive segment in nonactive row |Vnotcol - Vnotrow| = 1/3 Vmax.
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