Microchip Technology DM183037 Data Sheet

PIC18F97J94 FAMILY

DS30575A-page 264

 2012 Microchip Technology Inc.

13.8

LCD Multiplex Types

The LCD driver module can be configured into four
multiplex types:
• Static (only COM0 used)
• 1/2 multiplex (COM0 and COM1 are used)
• 1/3 multiplex (COM0, COM1 and COM2 are used)
• 1/4 multiplex (COM0, COM1, COM2 and COM3

are used)

• 1/5 multiplex (COM0, COM1, COM2, COM3 and

COM4 are used)

• 1/6 multiplex (COM0, COM1, COM2, COM3,

COM4 and COM5 are used)

• 1/7 multiplex (COM0, COM1, COM2, COM3,

COM4, COM5 and COM6 are used)

• 1/8 multiplex (COM0, COM1, COM2, COM3,

COM4, COM5, COM6 and COM7 are used)

The LMUX<2:0> setting (LCDCON<2:0>) decides the
function of the COM pins. (For details, see

Table 13-4

If the pin is a digital I/O, the corresponding TRIS bit
controls the data direction. If the pin is a COM drive, the
TRIS setting of that pin is overridden.

13.9

Segment Enables

The LCDSEx registers are used to select the pin function
for each segment pin. The selection allows each pin to
operate as either an LCD segment driver or a digital only
pin. To configure the pin as a segment pin, the corre-
sponding bits in the LCDSEx registers must be set to ‘1’.
If the pin is a digital I/O, the corresponding TRIS bit
controls the data direction. Any bit set in the LCDSEx
registers overrides any bit settings in the corresponding
TRIS register.

13.10 Pixel Control

The LCDDATAx registers contain bits that define the
state of each pixel. Each bit defines one unique pixel.

Table 13-2

shows the correlation of each bit in the

LCDDATAx registers to the respective common and
segment signals.
Any LCD pixel location not being used for display can
be used as general purpose RAM.

13.11 LCD Frame Frequency

The rate at which the COM and SEG outputs change is
called the LCD frame frequency.

Note:

On a Power-on Reset, the LMUX<2:0>
bits are ‘000’.

TABLE 13-4:

COM<7:0> PIN FUNCTIONS

LMUX<2:0>

COM7 Pin COM6 Pin COM5 Pin COM4 Pin COM3 Pin COM2 Pin COM1 Pin COM0 Pin

111

COM7

COM6

COM5

COM4

COM3

COM2

COM1

COM0

110

I/O Pin

COM6

COM5

COM4

COM3

COM2

COM1

COM0

101

I/O Pin

COM5

COM4

COM3

COM2

COM1

COM0

100

I/O Pin

COM4

COM3

COM2

COM1

COM0

011

I/O Pin

COM3

COM2

COM1

COM0

010

I/O Pin

COM2

COM1

COM0

001

I/O Pin

COM1

COM0

000

I/O Pin

COM0

Note:

Pins, COM<7:4>, can also be used as SEG pins when ¼ multiplex to static multiplex are used. These pins
can be used as I/O pins only if respective bits in the LCDSEx registers are set to ‘0’.

Note:

On a Power-on Reset, these pins are
configured as digital I/O.

TABLE 13-5:

FRAME FREQUENCY FORMULAS

Multiplex

Frame Frequency =

Static (‘000’)

Clock Source/(4 x 1 x (LP<3:0> + 1))

1/2 (‘001’)

Clock Source/(2 x 2 x (LP<3:0> + 1))

1/3 (‘010’)

Clock Source/(1 x 3 x (LP<3:0> + 1))

1/4 (‘011’)

Clock Source/(1 x 4 x (LP<3:0> + 1))

1/5 (‘100’)

Clock Source/(1 x 5 x (LP<3:0> + 1))

1/6 (‘101’)

Clock Source/(1 x 6 x (LP<3:0> + 1))

1/7 (‘110’)

Clock Source/(1 x 7 x (LP<3:0> + 1))

1/8 (‘111’)

Clock Source/(1 x 8 x (LP<3:0> + 1))

Note: The clock source is FRC/8192, SOSC/32 or LPRC/32.