Rainbow-electronics Atmega169L Manual de usuario descargar pdf (Pagina 210)

210

ATmega169V/L

2514A–AVR–08/02

Figure 96. Block Diagram LCD Module

LCD Clock Cources The LCD Controller can be clocked by an internal synchronous or an external asynchro-

nous clock source. The clock source clk

LCD

is by default equal to the system clock, clk

I/O

When the LCDCS bit in the LCDCRB Register is written to logic one, the clock source is

takenfromtheTOSC1pin.

The clock source must be stable to obtain accurate LCD timing and hence minimize DC

voltage offset across LCD segments.

LCD Prescaler The prescaler consist of a 12-bit ripple counter and a 1- to 8-clock divider. The

LCDPS2:0 bits selects clk

LCD

divided by 16, 64, 128, 256, 512, 1024, 2048, or 4096.

If a finer resolution rate is required, the LCDCD2:0 bits can be used to divide the clock

further by 1 to 8.

Output from the clock divider clk

LCD_PS

is used as clock source for the LCD timing.

LCD Memory The display memory is available through I/O Registers grouped for each common termi-

nal. When a bit in the display memory is written to one, the corresponding segment is

energized (on), and non-energized when a bit in the display memory is written to zero.

To energize a segment, an absolute voltage above a certain threshold must be applied.

This is done by letting the output voltage on corresponding COM pin and SEG pin have

opposite phase. For display with more than one common, one (1/2 bias) or two (1/3

bias) additional voltage levels must be applied. Otherwise, non-energized segments on

COM0 would be energized for all non-selected common.

Clock

Multiplexer

12-bit Prescaler

Divide by 1 to 8

LCD

Timing

LCDCRB

LCDFRR

clk

i/o

TOSC

LCDCRA

clk

LCD

/4096

clk

LCD

/2048

clk

LCD

/128

clk

LCD

/1024

clk

LCD

/512

clk

LCD

/256

clk

LCD

/64

clk

LCD

/16

Analog

Switch

Array

lcdcs

lcdcd2:0

lcdps2:0

clk

LCD

SEG0

SEG1

SEG2

SEG3

SEG4

SEG5

SEG6

SEG7

SEG8

SEG9

SEG10

SEG11

SEG12

SEG13

SEG14

SEG15

SEG16

SEG17

SEG18

SEG19

SEG20

SEG21

SEG22

SEG23

SEG24

COM0

COM1

COM2

COM3

LCD Buffer/

Driver

LCD

LCDDR 18 -15

LCDDR 13 -10

LCDDR 8 - 5

LCDDR 3 - 0

LATCH

array

LCD Ouput

Decoder

LCDCCR

lcdcc3:0

Contrast Controller/

Power Supply

clk

LCD_PS

LCD

CAP

25 x

4:1

MUX

LCD_voltage_ok

2/3 V

LCD

1/2 V

LCD

1/3 V

LCD

1 2 ... 205 206 207 208 209 210 211 212 213 214 215 ... 316 317

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