PIC16F1938_13 Datasheet, PDF (340/488 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver

PIC16(L)F1938/9
27.6 LCD Multiplex Types
The LCD Driver module can be configured into one of
four multiplex types:
• Static (only COM0 is used)
• 1/2 multiplex (COM<1:0> are used)
• 1/3 multiplex (COM<2:0> are used)
• 1/4 multiplex (COM<3:0> are used)
The LMUX<1:0> bit setting of the LCDCON register
decides which of the LCD common pins are used (see
Table 27-4 for details).
If the pin is a digital I/O, the corresponding TRIS bit
controls the data direction. If the pin is a COM drive,
then the TRIS setting of that pin is overridden.
TABLE 27-4: COMMON PIN USAGE
Multiplex
LMUX
<1:0>
COM3
COM2
COM1
Static
1/2
1/3
1/4
00 Unused Unused Unused
01 Unused Unused Active
10 Unused Active Active
11
Active Active Active
27.7 Segment Enables
The LCDSEn 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
as one of the pin’s alternate functions. To configure the
pin as a segment pin, the corresponding bits in the
LCDSEn 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 LCDSEn
registers overrides any bit settings in the corresponding
TRIS register.
Note: On a Power-on Reset, these pins are
configured as normal I/O, not LCD pins.
27.8 Pixel Control
The LCDDATAx registers contain bits which define the
state of each pixel. Each bit defines one unique pixel.
Register 27-6 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.
27.9 LCD Frame Frequency
The rate at which the COM and SEG outputs change is
called the LCD frame frequency.
TABLE 27-5: FRAME FREQUENCY
FORMULAS
Multiplex
Frame Frequency =
Static
1/2
1/3
1/4
Note:
Clock source/(4 x 1 x (LCD Prescaler) x
32))
Clock source/(2 x 2 x (LCD Prescaler) x
32))
Clock source/(1 x 3 x (LCD Prescaler) x
32))
Clock source/(1 x 4 x (LCD Prescaler) x
32))
Clock source is FOSC/256, T1OSC or
LFINTOSC.
TABLE 27-6:
APPROXIMATE FRAME
FREQUENCY (IN Hz) USING
FOSC @ 8 MHz, TIMER1 @
32.768 kHz OR LFINTOSC
LP<3:0>
Static
1/2
1/3
1/4
2
122
122 162 122
3
81
81
108
81
4
61
61
81
61
5
49
49
65
49
6
41
41
54
41
7
35
35
47
35
DS40001574C-page 340
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