Datasheet

Liquid Crystal Display (LCD) Driver
Functional Description
MC68HC908LJ24/LK24 — Rev. 2.1 Data Sheet
Freescale Semiconductor Liquid Crystal Display (LCD) Driver 353
17.5 Functional Description
Figure 17-2 shows a block diagram of the LCD driver module, and
Figure 17-3 shows a simplified schematic of the LCD system.
The LCD driver module uses a 1/3 biasing method. The LCD power is
supplied by the V
LCD
pin. Voltages V
LCD1
, V
LCD2
, and V
LCD3
are
generated by an internal resistor ladder.
The LCD data registers, LDAT1–LDAT17, control the LCD segments’
ON/OFF, with each data register controlling two frontplanes. When a
logic 1 is written to a FxBx bit in the data register, the corresponding
frontplane-backplane segment will turn ON. When a logic 0 is written, the
the segment will turn OFF.
When the LCD driver module is disabled (LCDE = 0), the LCD display
will be OFF, all backplane and frontplane drivers have the same
potential as V
DD
. The resistor ladder is disconnected from V
DD
to reduce
power consumption.
Figure 17-2. LCD Block Diagram
LCD FRONTPLANE DRIVER AND DATA LATCH
PORT-C LOGIC
BACKPLANE
DRIVER
LCDE (LCDC)
STATE
CONTROL
1/41/3
1/3
1/4
1/1
PTC7/FP26
PTC6/FP25
PTC5/FP24
PTC4/FP23
PTC3/FP22
PTC2/FP21
PTC1/FP20
PTC0/FP19
FP5 FP6 FP7 FP8 FP9 FP10 PTE0/FP11 PTE1/FP12 PTE2/FP13 PTE3/FP14 PTE4/FP15 PTE5/FP16 PTE6/FP17 PTE7/FP18
BP0
BP1
BP2
FP0/BP3
FP1
FP2
FP3
FP4
INTERNAL BUS
PORT-E LOGIC
FP32
FP31
FP30
FP29
FP28
FP27