HT56R656 datasheet(37/108 Pages) HOLTEK

37 / 108 page

HT56R62/HT56R65

HT56R642/HT56R644/HT56R654/HT56R656

Rev. 1.00

July 20, 2009

Programming Considerations

Certain precautions must be taken when programming

the LCD/LED. One of these is to ensure that the Display

Memory is properly initialised after the microcontroller is

powered on. Like the General Purpose Data Memory,

the contents of the Display Memory are in an unknown

condition after power-on. As the contents of the Display

Memory y will be mapped into the actual display, it is im-

portant to initialise this memory area into a known condi-

tion soon after applying power to obtain a proper display

pattern.

Consideration must also be given to the capacitive load

of the actual LCD used in the application. As the load

presented to the microcontroller by LCD pixels can be

generally modeled as mainly capacitive in nature, it is

important that this is not excessive, a point that is partic-

ularly true in the case of the COM lines which may be

connected to many LCD pixels. The accompanying dia-

gram depicts the equivalent circuit of the LCD.

One additional consideration that must be taken into ac-

count is what happens when the microcontroller enters a

Power Down condition. The LCDEN control bit in the

LCDCTRL or LEDEN bit in the LEDCTRL register per-

mits the display to be powered off to reduce power con-

sumption. If this bit is zero, the driving signals to the

display will cease, producing a blank display pattern but

reducing any power consumption associated with the

LCD.

After Power-on, note that as the LCDEN and LEDEN

bits will be cleared to zero, the display function will be

disabled.

The accompanying timing diagrams depict the display

driver signals generated by the microcontroller for vari-

ous values of duty and bias. The huge range of various

permutations only permit a few types to be displayed

here.

V S S

V D D

V S S

V D D

C O M 0 i n

l o w a c t i v e

S E G i n

l o w a c t i v e

C O M 0 i n

l o w a c t i v e

S E G i n

h i g h a c t i v e

C O M 0 i n

h i g h a c t i v e

S E G i n

l o w a c t i v e

C O M 0 i n

h i g h a c t i v e

S E G i n

h i g h a c t i v e

V S S

V D D

V S S

V D D

V S S

V D D

V S S

V D D

V S S

V D D

V S S

V D D

5 5

LED Static Mode Normal Operation

V S S

V D D

V S S

V D D

V S S

V D D

C O M 0

C O M 1

S E G

LED 1/4 Duty, COM High Active,

SEG Low Active, Display Off

C O M 0

C O M 1

C O M 2

C O M n

S E G 0

S E G 1

S E G 2

S E G n

LCD Panel Equivalent Circuit

HT56R656 bảng dữ liệu(PDF) 37 Page - Holtek Semiconductor Inc

HT56R656 bảng dữ liệu(HTML) 37 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

bảng dữ liệu tải về

Link URL