Datasheet

 2010 Microchip Technology Inc. DS39770C-page 187
PIC18F85J90 FAMILY
16.10 Operation During Sleep
The LCD module can operate during Sleep. The selec-
tion is controlled by the SLPEN bit (LCDCON<6>).
Setting the SLPEN bit allows the LCD module to go to
Sleep. Clearing the SLPEN bit allows the module to
continue to operate during Sleep.
If a SLEEP instruction is executed and SLPEN = 1, the
LCD module will cease all functions and go into a very
low-current consumption mode. The module will stop
operation immediately and drive the minimum LCD
voltage on both segment and common lines.
Figure 16-18 shows this operation.
To ensure that no DC component is introduced on the
panel, the SLEEP instruction should be executed imme-
diately after a LCD frame boundary. The LCD interrupt
can be used to determine the frame boundary. See
Section 16.9 “LCD Interrupts” for the formulas to
calculate the delay.
If a SLEEP instruction is executed and SLPEN = 0, the
module will continue to display the current contents of
the LCDDATA registers. To allow the module to
continue operation while in Sleep, the clock source
must be either the Timer1 oscillator or one of the
internal oscillators (either INTRC or INTOSC as the
default system clock). While in Sleep, the LCD data
cannot be changed. The LCD module current
consumption will not decrease in this mode; however,
the overall consumption of the device will be lower due
to shut down of the core and other peripheral functions.
If the system clock is selected and the module is not
configured for Sleep operation, the module will ignore
the SLPEN bit and stop operation immediately. The
minimum LCD voltage will then be driven onto the
segments and commons
16.10.1 USING THE LCD REGULATOR
DURING SLEEP
Applications that use the LCD regulator for bias
generation may not achieve the same degree of power
reductions in Sleep mode when compared to applica-
tions using Mode 3 (resistor ladder) biasing. This is
particularly true with Mode 0 operation, where the
charge pump is active.
If Modes 0, 1 or 2 are used for bias generation,
software contrast control will not be available.
FIGURE 16-18: SLEEP ENTRY/EXIT WHEN SLPEN = 1 OR CS<1:0> = 00
SLEEP Instruction Execution
Wake-up
2 Frames
V
3
V
2
V
1
V
0
V
3
V
2
V
1
V
0
V
3
V
2
V
1
V
0
V
3
V
2
V
1
V
0
COM0
COM1
COM2
SEG0