PIC18F87K90 Datasheet, PDF (283/566 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt XLP Technology

PIC18F87K90 FAMILY
20.3.2.3 Internal Reference
Under firmware control, an internal reference for the
LCD bias voltages can be enabled. When enabled, the
source of this voltage can be VDD.
When no internal reference is selected, the LCD
contrast control circuit is disabled and LCD bias must
be provided externally. Whenever the LCD module is
inactive (LCDA = 0), the internal reference will be
turned off.
20.3.2.4 VLCDx Pins
The VLCD3, VLCD2 and VLCD1 pins provide the
ability for an external LCD bias network to be used
instead of the internal ladder. Use of the VLCDx pins
does not prevent use of the internal ladder.
Each VLCD pin has an independent control in the
LCDREF register, allowing access to any or all of the
LCD bias signals.
This architecture allows for maximum flexibility in
different applications. The VLCDx pins could be used
to add capacitors to the internal reference ladder for
increasing the drive capacity. For applications where
the internal contrast control is insufficient, the firmware
can choose to enable only the VLCD3 pin, allowing an
external contrast control circuit to use the internal
reference divider.
20.4 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)
The LMUX<1:0> setting (LCDCON<1:0>) decides the
function of the PORTE<6:4> bits. (For details, see
Table 20-4.)
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.
Note: On a Power-on Reset, the LMUX<1:0>
bits are ‘00’.
TABLE 20-4: PORTE<6:4> FUNCTION
LMUX<1:0> PORTE<6> PORTE<5> PORTE<4>
00
Digital I/O Digital I/O Digital I/O
01
Digital I/O Digital I/O COM1 Driver
10
Digital I/O COM2 Driver COM1 Driver
11
COM3 Driver COM2 Driver COM1 Driver
20.5 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 corresponding 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.
Note: On a Power-on Reset, these pins are
configured as digital I/O.
20.6 Pixel Control
The LCDDATAx registers contain bits that define the
state of each pixel. Each bit defines one unique pixel.
Table 20-2 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.
 2010 Microchip Technology Inc.
Preliminary
DS39957B-page 283