PIC16F946-ESLASHMLQTP datasheet(166/330 Pages) MICROCHIP

166 / 330 page

PIC16F913/914/916/917/946

DS41250F-page 164

10.9

LCD Interrupts

The LCD timing generation provides an interrupt that

defines the LCD frame timing.

A new frame is defined to begin at the leading edge of

the COM0 common signal. The interrupt will be set

immediately after the LCD controller completes access-

ing all pixel data required for a frame. This will occur at

a fixed interval before the frame boundary (TFINT), as

shown in Figure 10-17. The LCD controller will begin to

access data for the next frame within the interval from

the interrupt to when the controller begins to access

data after the interrupt (TFWR). New data must be writ-

ten within TFWR, as this is when the LCD controller will

begin to access the data for the next frame.

When the LCD driver is running with Type-B waveforms

and the LMUX<1:0> bits are not equal to ‘00’ (static

drive), there are some additional issues that must be

addressed. Since the DC voltage on the pixel takes two

frames to maintain zero volts, the pixel data must not

change between subsequent frames. If the pixel data

were allowed to change, the waveform for the odd

frames would not necessarily be the complement of the

waveform generated in the even frames and a DC

component would be introduced into the panel.

Therefore, when using Type-B waveforms, the user

must synchronize the LCD pixel updates to occur within

a subframe after the frame interrupt.

To correctly sequence writing while in Type-B, the

interrupt will only occur on complete phase intervals. If

the user attempts to write when the write is disabled,

the WERR bit of the LCDCON register is set and the

write does not occur.

FIGURE 10-17:

WAVEFORMS AND INTERRUPT TIMING IN QUARTER-DUTY CYCLE DRIVE

(EXAMPLE – TYPE-B, NON-STATIC)

Note:

The interrupt is not generated when the

Type-A waveform is selected and when the

Type-B with no multiplex (static) is

selected.

Frame

Boundary

Frame

Boundary

LCD

Interrupt

Occurs

Controller Accesses

Next Frame Data

TFINT

TFWR

TFWR =TFRAME/2*(LMUX<1:0> + 1) + TCY/2

TFINT =(TFWR/2 – (2 TCY + 40 ns))

→ minimum = 1.5(TFRAME/4) – (2 TCY + 40 ns)

(TFWR/2 – (1 TCY + 40 ns))

→ maximum = 1.5(TFRAME/4) – (1 TCY + 40 ns)

Frame

Boundary

COM0

COM1

COM2

COM3

2 Frames

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