Datasheet

PIC16(L)F1934/6/7
DS41364E-page 334  2008-2011 Microchip Technology Inc.
27.2 LCD Clock Source Selection
The LCD module has 3 possible clock sources:
•F
OSC/256
•T1OSC
•LFINTOSC
The first clock source is the system clock divided by
256 (F
OSC/256). 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 LP<3:0> of the LCDPS register are used
to set the LCD frame clock rate.
The second clock source is the T1OSC. 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 bit of the T1CON register
should be set.
The third clock source is the 31 kHz LFINTOSC, 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 bits CS<1:0> of the LCDCON register can select
any of these clock sources.
27.2.1 LCD PRESCALER
A 4-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 of the LCDPS register,
which determine the prescaler assignment and prescale
ratio.
The prescale values are selectable from 1:1 through
1:16.
FIGURE 27-2: LCD CLOCK GENERATION
CS<1:0>
T1OSC 32 kHz
Crystal Osc.
LFINTOSC
Nominal = 31 kHz
Static
1/2
1/3,
1/4
÷4
LMUX<1:0>
4-bit Prog
÷1, 2, 3, 4
Ring Counter
COM0 COM1 COM2 COM3
÷256
FOSC
÷2
÷ 32
LP<3:0>
Prescaler
To Ladder
Power Control
Segment
Clock
Counter