HT56R66 Holtek Semiconductor Inc., HT56R66 Datasheet - Page 28

• Manufacturer Part Number: HT56R66
• Description: Tinypower Tm A/d Type With Lcd 8-bit Otp Mcu
• Manufacturer: Holtek Semiconductor Inc.

Programming Considerations
Within the user program, one of the first things to con-
sider is port initialisation. After a reset, all of the I/O data
and port control registers will be set high. This means
that all I/O pins will default to an input state, the level of
which depends on the other connected circuitry and
whether pull-high selections have been chosen. If the
port control registers, PAC, PBC, PCC and PDC, are
then programmed to setup some pins as outputs, these
output pins will have an initial high output value unless
the associated port data registers, PA, PB, PC and PD,
are first programmed. Selecting which pins are inputs
and which are outputs can be achieved byte-wide by
loading the correct values into the appropriate port con-
trol register or by programming individual bits in the port
control register using the SET [m].i and CLR [m].i in-
structions. Note that when using these bit control in-
structions, a read-modify-write operation takes place.
The microcontroller must first read in the data on the en-
tire port, modify it to the required new bit values and then
rewrite this data back to the output ports.
Port A has the additional capability of providing wake-up
functions. When the device is in the Power Down Mode,
various methods are available to wake the device up.
One of these is a high to low transition of any of the Port
A pins. Single or multiple pins on Port A can be setup to
have this function.
Rev. 1.10
Read/Write Timing
28
LCD and LED Driver
For large volume applications, which incorporate an
LCD in their design, the use of a custom display rather
than a more expensive character based display reduces
costs significantly. However, the corresponding COM
and SEG signals required, which vary in both amplitude
and time, to drive such a custom display require many
special considerations for proper LCD operation to oc-
cur. These devices all contain an LCD Driver function,
which with their internal LCD signal generating circuitry
and various options, will automatically generate these
time and amplitude varying signals to provide a means
of direct driving and easy interfacing to a range of cus-
tom LCDs.
Additionally some of the devices also include LED driver
circuitry which can generated the required signals to
drive the COM and SEGMENT signals for LED panels.
All device include a wide range of options to enable LCD
and LED displays of various types to be driven. The ta-
ble shows the range of options available across the de-
vice range.
Note:
HT56R66
HT56R666
HT56R666
Part No.
Device
The HT56R66 device do not have an LED driver
function.
Duty
1/16
1/2
1/3
1/4
1/8
LCD Selections
LED Duty
LED Selections
Static
1/12
1/16
1/4
1/8
HT56R66/HT56R666
Driver
48 16
49 2
49 3
48 4
56 8
No.
Bias
1/3,
1/4
1/5
1/2
1/3
or
or
LED Driver No.
September 8, 2009
Type
48 12
48 16
Bias
56 1
56 4
56 8
or
C
R
R
Wave
Type
or
or
A
B
A
B