INTEDG datasheet(365/478 Pages) MICROCHIP

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DS41414D-page 365

PIC16(L)F1946/47

27.13 Operation During Sleep

The LCD module can operate during Sleep. The

selection is controlled by bit SLPEN of the LCDCON

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 27-20 shows this operation.

The LCD module can be configured to operate during

Sleep. The selection is controlled by bit SLPEN of the

LCDCON register. Clearing SLPEN and correctly con-

figuring the LCD module clock will allow the LCD mod-

ule to operate during Sleep. Setting SLPEN and

correctly executing the LCD module shutdown will

disable the LCD module during Sleep and save power.

If a SLEEP instruction is executed and SLPEN = 1, the

LCD module will immediately cease all functions, drive

the outputs to Vss and go into a very low-current mode.

The SLEEP instruction should only be executed after

the LCD module has been disabled and the current

cycle completed, thus ensuring that there are no DC

voltages on the glass. To disable the LCD module,

clear the LCDEN bit. The LCD module will complete the

disabling process after the current frame, clear the

LCDA bit and optionally cause an interrupt.

The steps required to properly enter Sleep with the

LCD disabled are:

• Clear LCDEN

• Wait for LCDA = 0 either by polling or by interrupt

• Execute SLEEP

If SLPEN = 0 and SLEEP is executed while the LCD

module clock source is FOSC/4, then the LCD module

will halt with the pin driving the last LCD voltage pat-

tern. Prolonged exposure to a fixed LCD voltage pat-

tern will cause damage to the LCD glass. To prevent

LCD glass damage, either perform the proper LCD

module shutdown prior to Sleep, or change the LCD

module clock to allow the LCD module to continue

operation during Sleep.

If a SLEEP instruction is executed and SLPEN = 0 and

the LCD module clock is either T1OSC or LFINTOSC,

the module will continue to display the current contents

of the LCDDATA registers. While in Sleep, the LCD

data cannot be changed. If the LCDIE bit is set, the

device will wake from Sleep on the next LCD frame

boundary. The LCD module current consumption will

not decrease in this mode; however, the overall device

power consumption will be lower due to the shutdown

of the CPU and other peripherals.

Table 27-8 shows the status of the LCD module during

a Sleep while using each of the three available clock

sources.

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 LFINTOSC or T1OSC external

oscillator. 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.

Table 27-8 shows the status of the LCD module during

Sleep while using each of the three available clock

sources:

TABLE 27-8:

LCD MODULE STATUS

DURING SLEEP

If LCD interrupts are being generated (Type-B wave-

form with a multiplex mode not static) and LCDIE = 1,

the device will awaken from Sleep on the next frame

boundary.

Note:

When the LCDEN bit is cleared, the LCD

module will be disabled at the completion

of frame. At this time, the port pins will

revert to digital functionality. To minimize

power consumption due to floating digital

inputs, the LCD pins should be driven low

using the PORT and TRIS registers.

Clock Source

SLPEN

Operational

During Sleep

T1OSC

Yes

LFINTOSC

Yes

FOSC/4

Note:

The LFINTOSC or external T1OSC

oscillator must be used to operate the

LCD module during Sleep.

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