XC68HC705F32 Motorola, XC68HC705F32 Datasheet - Page 85

• Manufacturer Part Number: XC68HC705F32
• Description: MICROCONTROLLER
• Manufacturer: Motorola

8.2
The LCD driver module can operate in four modes providing different multiplex ratios and number
of backplanes as follows:
•
•
•
•
The operating mode is selected at power on using the multiplex ratio bits (MUX3 and MUX4) in
the LCD control register as shown in
It is recommended that the EXTVON and INTVLCD bits in the LCD register are not set (display is
disabled) until the multiplex rate is selected. The voltage levels required for the different multiplex
rates are generated internally by a resistive divider chain between V
The 2-way multiplex with 1/3 bias and the three and four-way multiplex options require four voltage
levels, whereas the two-way multiplex with 1/2 bias needs only three levels. Resistors R1, R2 and
R3 are valued at 20k
produce the various LCD waveforms outlined in
The LCD drivers can operate with an external V
generated LCD voltage when INTVLCD = 1. The EXTVON option is useful when a display with
particular thresholds is being used. The LCD controller is enabled if the EXTVON bit or the
INTVLCD bit is set.
EXTVON and INTVLCD of the LCD control register.
Note:
Note:
.
MC68HC05F32
1/2 bias, 2 backplanes
1/3 bias, 2 backplanes
1/3 bias, 3 backplanes
1/4 bias, 4 backplanes
The external voltage V
If both bits INTVLCD and EXTVON are set, an externally applied voltage source can
cause damage to the LCD drivers.
LCD operation
Table 8-2
EXTVON INTVLCD
LIQUID CRYSTAL DISPLAY DRIVER MODULE
40%.
0
0
1
1
Table 8-2 LCD controller operating modes
Figure 8-2
shows the different modes of operation depending on the bits
LCD
0
1
0
1
Table
may not exceed the positive power supply voltage, V
controller
shows the resistive divider chain network that is used to
LCD
on
on
on
off
8-4.
LCD
Section
Internal voltage
generator
supply when EXTVON = 1, or with an internally
on
on
off
off
8.3.
connected with
Resistor chain
internal V
both (for test)
VLCD pin
—
LCD
LCD
and V
SS
.
MOTOROLA
DD
TPG
.
8-3
8