PIC16F946 Datasheet, PDF (115/274 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

PIC16F946
9.7 LCD Waveform Generation
LCD waveforms are generated so that the net AC
voltage across the dark pixel should be maximized and
the net AC voltage across the clear pixel should be
minimized. The net DC voltage across any pixel should
be zero.
The COM signal represents the time slice for each
common, while the SEG contains the pixel data.
The pixel signal (COM-SEG) will have no DC compo-
nent and it can take only one of the two rms values. The
higher rms value will create a dark pixel and a lower
rms value will create a clear pixel.
As the number of commons increases, the delta
between the two rms values decreases. The delta
represents the maximum contrast that the display can
have.
The LCDs can be driven by two types of waveform:
Type-A and Type-B. In Type-A waveform, the phase
changes within each common type, whereas in Type-B
waveform, the phase changes on each frame
boundary. Thus, Type-A waveform maintains ‘0’ VDC
over a single frame, whereas Type-B waveform takes
two frames.
Note 1: If Sleep has to be executed with LCD
Sleep enabled (LCDCON<SLPEN> is
‘1’), then care must be taken to execute
Sleep only when VDC on all the pixels is
‘0’.
2: When the LCD clock source is FOSC/8192,
if Sleep is executed, irrespective of the
LCDCON<SLPEN> setting, the LCD goes
into Sleep. Thus, take care to see that VDC
on all pixels is ‘0’ when Sleep is executed.
Figure 9-6 through Figure 9-16 provide waveforms for
static, half-multiplex, one-third-multiplex and
quarter-multiplex drives for Type-A and Type-B
waveforms.
FIGURE 9-6:
TYPE-A/TYPE-B WAVEFORMS IN STATIC DRIVE
V₁
COM0
COM0
V₀
V₁
SEG0
V₀
V₁
SEG1
V₀
V₁
COM0-SEG0
V₀
-V₁
COM0-SEG1
V₀
1 Frame
© 2005 Microchip Technology Inc.
Preliminary
DS41265A-page 113