HT56R666 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT56R666' PDF : 104 Pages View PDF
VDD
COM 0
VSS
VDD
COM 1
VSS
VDD
SEG
VSS
LED 1/4 Duty, COM High Active,
SEG Low Active, Display Off
0
12 3
71
C O M 0 in
VDD
lo w a c tiv e
VSS
S E G in
VDD
lo w a c tiv e
VSS
C O M 0 in
VDD
lo w a c tiv e
VSS
S E G in
VDD
h ig h a c tiv e
VSS
C O M 0 in
VDD
h ig h a c tiv e
VSS
S E G in
VDD
lo w a c tiv e
VSS
C O M 0 in
VDD
h ig h a c tiv e
VSS
S E G in
VDD
h ig h a c tiv e
VSS
LED Static Mode Normal Operation
HT56R66/HT56R666
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.
SEG 0
COM 0
SEG 1 SEG 2
COM 1
COM 2
SEG n
COM n
LCD Panel Equivalent Circuit
Rev. 1.40
35
May 11, 2012
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