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Microcontrollers with
integrated drivers are
providing a boost for the
growing LCD market
Liquid crystal displays (LCDs) have
soared in popularity in recent years
thanks to numerous advantages
over other display technologies.
Controlling them has also become
easier because of the introduction of
8bit microcontrollers with integrated
LCD drivers. Prominent features of
such LCD controllers include contrast
control, drive waveforms, biasing
methods and power modes.
These devices can directly drive
segmented displays with letters,
numbers, characters and icons and
have been developed to meet low-cost
design requirements. A good example
are the PIC microcontrollers from
Microchip, which are available in 28-,
Crystal clear choice for displays
Mary Tamar Tan, Applications Engineer at Microchip Technology, Rodger Richey,
Director Engineering and New Product Development at Microchip Technology
operation of the module. Once the
module is configured, the LCDEn
bit is used to enable or disable the
LCD module. The LCD panel can
also operate during sleep mode
by clearing the SLPEn bit. The bits
determine the LCD clock source and
the configuration must comply with
the LCD glass driving scheme.
The LCDPS configures the LCD clock
source prescaler and the type of
waveform. The prescaler select bits
have a direct effect on the LCD frame
frequency, so must be set accordingly
to avoid ghosting or flickering on the
display.
The LCDSEx configure the functions of
the port pins. Setting the segment enable
bit for a particular segment configures
that pin as an LCD driver. Likewise,
clearing the segment enable bit allows
the pin to function as an IO port.
40-, 64-, 80- and 100-pin packages
and can eliminate the need for several
external hardware components.
The LCD driver module generates
the timing control to drive a static or
multiplexed LCD panel with support
for up to 64 segments multiplexed
with up to four or eight commons.
Fig. 1 shows a typical LCD module
block diagram.
The number of LCD registers varies
depending on the maximum number
of commons and segments that can
be driven by the specific device.
Timing control block
As shown in Fig. 1, the timing
control block comprises the LCD
control register (LCDCON), LCD
phase register (LCDPS) and LCD
segment enable registers (LCDSEx).
The LCDCON controls the overall
38 l New-Tech Magazine Europe