MC68HC08LT8 Datasheet, PDF (77/156 Pages) Freescale Semiconductor, Inc – Microcontrollers

Functional Description
8.4 Functional Description
Figure 8-2 shows a block diagram of the LCD driver module, and Figure 8-3 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–LDAT13, 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 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.
PTB7/FP2
PTB6/FP1
FP0/BP3
BP2
BP1
BP0
PORT-E LOGIC
PORT-D LOGIC
LCD FRONTPLANE DRIVER AND DATA LATCH
1/3
1/4
LCDE (LCDCR)
STATE
CONTROL
1/1 1/3 1/4
Figure 8-2. LCD Block Diagram
PTC0/FP19
PTC1/FP20
PTC2/FP21
PTC3/FP22
PTC4/FP23
PTC5/FP24
MC68HC08LT8 Data Sheet, Rev. 1
Freescale Semiconductor
77