PIC18F6390 Datasheet, PDF (264/412 Pages) Microchip Technology – 64/80-Pin Flash Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F6390/6490/8390/8490
22.2 LCD Clock Source Selection
The LCD driver module has 3 possible clock sources:
• (FOSC/4)/8192
• T13CKI-Clock/32
• INTRC/32
The first clock source is the system clock divided by
8192 ((FOSC/4)/8192). This divider ratio is chosen to
provide about 1 kHz output when the system clock is
8 MHz. 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 Timer1 oscillator/32.
This also gives about 1 kHz when a 32.768 kHz crystal
is used with the Timer1 oscillator. To use the Timer1
oscillator as a clock source, the T1OSCEN
(T1CON<3>) bit should be set.
FIGURE 22-2:
LCD CLOCK GENERATION
The third clock source is a 31.25 kHz internal RC
oscillator/32, which 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.
Using the bits, CS1:CS0 (LCDCON<3:2>), any of these
clock sources can be selected.
22.2.1 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 LP3:LP0 bits (LCDPS<3:0>), which
determine the prescaler assignment and prescale ratio.
The prescale values from 1:1 through 1:32768 in
power-of-2 increments are selectable.
System Clock
(FOSC/4)
÷8192
TMR1 32 kHz
÷32
Crystal Oscillator
Internal RC Oscillator
Nom FRC = 31.25 kHz
÷32
CS1:CS0
(LCDCON<3:2>)
÷4
STAT
÷2
DUP
4-bit Prog Prescaler
TRIP
QUAD
LP3:LP0
(LCDPS<3:0>)
LMUX1:LMUX0
(LCDCON<1:0>)
÷1, 2, 3, 4
Ring Counter
LMUX1:LMUX0
(LCDCON<1:0>)
DS39629B-page 262
Preliminary
 2004 Microchip Technology Inc.