Datasheet

Chapter 9 Liquid Crystal Display Driver (S08LCDV1)
MC9S08LC60 Series Data Sheet: Technical Data, Rev. 4
138 Freescale Semiconductor
9.4.1 LCD Driver Description
The LCD module driver has three modes of operation:
• 1/2 duty (2 backplanes), 1/3 bias (4 voltage levels)
• 1/3 duty (3 backplanes), 1/3 bias (4 voltage levels)
• 1/4 duty (4 backplanes), 1/3 bias (4 voltage levels)
Note all modes are 1/3 bias. These modes of operation are described in more detail in the following
sections.
9.4.1.1 LCD Duty Cycle
The duty cycle indicates the number of LCD panel segments capable of being driven by each individual
frontplane output driver. Depending on the duty cycle, the LCD waveform drive can be categorized as
either static or multiplex.
In static driving method, the LCD is driven with two square waveforms. The static driving method is the
most basic method to drive an LCD panel, but, because each frontplace driver can drive only one LCD
segment, static driving limits the number of LCD segments that can be driven. In static mode, only one
backplane is required.
In multiplex mode, the LCD waveforms are multi-level and depend on the bias mode. Multiplex mode,
depending on the number of backplanes, can drive multiple LCD segments with a single frontplane driver.
Multiplex mode is effective in reducing the number of driver circuits and the number of connections to
LCD segments. For multiplex mode operation, at least two backplane drivers are needed. The LCD module
is optimized for multiplex mode.
The duty cycle indicates the amount of time the LCD panel segment is energized during each LCD module
frame cycle. The denominator of the duty cycle indicates the number of backplanes that are being used to
drive an LCD panel. Therefore, the available duty cycle options for the LCD module are 1/2, 1/3, and 1/4.
The duty cycle is configured using the DUTY[1:0] bit field in the LCDCR0 register as shown in
Table 9-13.
Table 9-13. LCD Module Duty Cycle Modes
Duty
LCDCR0 Register Backplanes
DUTY1 DUTY0 BP3 BP2 BP1 BP0
1/2 0 1 OFF OFF BP1 BP0
1/3 1 0 OFF BP2 BP1 BP0
1/4 1 1 BP3 BP2 BP1 BP0
Reserved 0 0 N/A N/A N/A N/A