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CHAPTER 14 LCD CONTROLLER/DRIVER
14.3 Structure of LCD Controller/Driver
This section describes the pins, pin block diagrams, register, and display RAM of the
LCD controller/driver.
s LCD Controller/Driver Pins
The LCD controller/driver uses 4 common output pins (COM0 to COM3), 14 segment output pin
(SEG0 to SEG13) and 4 LCD driving power supply pins (V0 to V3).
r COM0, COM1, P70/COM2, and P71/COM3 Pins
P70/COM2 and P71/COM3 pins can function either as output-only ports (P70 and P71) and
LCD common output pins (COM2 and COM3). The selection, however is made by mask option
in MB89983 and by LCD control register 2 (LCR2) in MB89P985 and MB89PV980.
Check:
When the pins are used as LCD common outputs, the corresponding port data register bits
(PDR7: bits 0 and 1) should be set to "1" to turn the output transistor "off". (COM0 and
COM1 are dedicated LCD common output pins.)
r P40/SEG0 to P47/SEG7 and P60/SEG8 to P65/SEG13
P40/SEG0 to P47/SEG7 and P60/SEG8 to P65/SEG13 can function either as output-only ports
(P40 to P47 and P60 to P65) and LCD segment output pins (SEG0 to SEG7 and SEG8 to
SEG13). The selection, however is made by mask option in MB89983 and by LCD control
register 2 (LCR2) in MB89P985 and MB89PV980.
Check:
When these pins are used as LCD segment outputs, the corresponding port data registers
(PDR4 and PDR6) should be set to all "1s" to turn the output transistors off.
r V0 to V3
These pins are the LCD driving power supply pins.
s Block Diagrams of LCD Controller/Driver Pin
Figure 14.3-1 Block Diagram of LCD Controller/Driver Pin (Dedicated Common Output Pins)
Dedicated common output pins
Pin
COM0, COM1
Common control signal
LCD drive voltage (V3 or V2)
LCD drive voltage (V1 or V0)
Common control signal
V0 to V3: V0 to V3 pin voltages
N ch
P ch
N ch