NXP Semiconductors MC9S08LG16, Reference Manual

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Chapter 8 LCD Module (S08LCDLPV1)
MC9S08LG32 MCU Series, Rev. 5
Freescale Semiconductor 175
• Duty cycle (number of backplanes)
• Backplane assignment (which LCD[44:0] pins operate as backplanes)
• Frame frequency interrupt enable
• Blinking frequency and options
• Power-supply configurations
The LCD module also provides an LCD pin enable control. Setting the LCD pin enable bit (PEN[x] in the
LCDPEN[y] register) for a particular LCD[y] pin enables the LCD module functionality of that pin once
the LCDEN bit is set. When the BPEN[x] bit in the LCDBPEN[y] is set, the associated pin operates as a
backplane. The LCDWF registers can then activate (display) the corresponding LCD segments on an LCD
panel.
The LCDWF registers control the on/off state for the segments controlled by the LCD pins defined as front
planes and the active phase for the backplanes. Blank display modes do not use the data from the LCDWF
registers. When using the LCDWF register for frontplane operation, writing a 0 turns the segment off.
For pins enabled as backplane, the phase of the backplane (A-H) is assigned by the LCDWF register for
the corresponding backplane pin. For a detailed description of LCD module operation for a basic
seven-segment LCD display, see
Section 9.6.1, “LCD Seven Segment Example Description .”
9.4.1 LCD Driver Description
The LCD module driver has 8 modes of operation:
• 1/1 duty (1 backplane) (Phase A), 1/3 bias (4 voltage levels)
• 1/2 duty (2 backplanes) (Phase A, B), 1/3 bias (4 voltage levels)
• 1/3 duty (3 backplanes) (Phase A, B, C), 1/3 bias (4 voltage levels)
• 1/4 duty (4 backplanes) (Phase A, B, C, D), 1/3 bias (4 voltage levels)
• 1/5 duty (5 backplanes) (Phase A, B, C, D, E), 1/3 bias (4 voltage levels)
• 1/6 duty (6 backplanes) (Phase A, B, C, D, E, F), 1/3 bias (4 voltage levels)
• 1/7 duty (7 backplanes) (Phase A, B, C, D, E, F, G), 1/3 bias (4 voltage levels)
• 1/8 duty (8 backplanes) (Phase A, B, C, D, E, F, G, H), 1/3 bias (4 voltage levels)
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 denominator of 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 static or multiplexed.
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 frontplane driver can drive only one LCD
segment, static driving limits the LCD segments that can be driven with a given number of frontplane pins.
In static mode, only one backplane is required.