Datasheet

 2012 Microchip Technology Inc. DS30575A-page 251
PIC18F97J94 FAMILY
13.3 LCD Clock Source Selection
The LCD driver module has three possible clock
sources:
• FRC/8192
• SOSC Clock/32
• LPRC/32
The first clock source is the 8 MHz Fast Internal RC
(FRC) Oscillator divided by 8,192. This divider ratio is
chosen to provide about 1 kHz output. The divider is
not programmable. Instead, the LCD prescaler bits,
LCDPS<3:0>, are used to set the LCD frame clock
rate.
The second clock source is the SOSC Oscillator/32.
This also outputs about 1 kHz when a 32.768 kHz
crystal is used with the SOSC Oscillator. To use the
SOSC Oscillator as a clock source, set the SOSCEN
(T1CON<3>) bit.
The third clock source is a 31.25 kHz internal LPRC
Oscillator/32 that provides approximately 1 kHz output.
The second and third clock sources may be used to
continue running the LCD while the processor is in
Sleep.
These clock sources are selected through the bits,
CS<1:0> (LCDCON<4:3>).
13.3.1 LCD PRESCALER
A 16-bit counter is available as a prescaler for the LCD
clock. The prescaler is not directly readable or writable.
Its value is set by the LP<3:0> bits (LCDPS<3:0>) that
determine the prescaler assignment and prescale ratio.
Selectable prescale values are from 1:1 through 1:16,
in increments of one.
FIGURE 13-2: LCD CLOCK GENERATION
CS<1:0>
SOSC Oscillator
(32 kHz)
÷4
LMUX<2:0>
4-Bit Prog Prescaler
÷1, 2, 3....8
Ring Counter
LMUX<2:0>
COM0 COM1 COM2 COM7
÷8192
÷2
÷32
÷32
LP<3:0>
(LCDCON<4:2>) (LCDCON<2:0>)
(LCDCON<2:0>)
(LCDPS<3:0>)
FRC Oscillator
(8 MH
Z)
LPRC Oscillator
(31.25 kHz)
STAT
1/2 MUX
1/3 to 1/8
MUX