Microchip Technology dsPIC33 User Manual

dsPIC33/PIC24 Family Reference Manual
DS30009740B-page 8  2010-2013 Microchip Technology Inc.
4.0 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 (OSCCON<1>) 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>).
4.1 LCD Prescaler
A 16-bit counter is available as a prescaler for the LCD clock. The prescaler is not directly read-
able or writable. Its value is set by the LP<2:0> bits (LCDPS<2:0>) that determine the prescaler
assignment and prescale ratio.
Selectable prescale values are from 1:1 through 1:16, in increments of one.
Figure 4-1: LCD Clock Generation
CS<1:0>
SOSC Oscillator
(32 kHz)
LPRC Oscillator
(31.25 kHz)
÷4
LMUX<2:0>
4-Bit Prog Prescaler
÷1, 2, 3....8
Ring Counter
LMUX<2:0>
COM0 COM1 COM2 COM7
÷8192
(8 MH
Z)
÷2
÷32
÷32
LP<2:0>
(LCDCON<4:3>)
(LCDCON<2:0>)
(LCDCON< 2:0>)
(LCDPS<2:0>)
FRC Oscillator
STAT
1/2 MUX
MUX

Microchip Technology dsPIC33 Specifications

General

Brand	Microchip Technology
Model	dsPIC33
Category	I/O Systems
Language	English