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HT1647A

64x16 LCD Controller for I/O MCU

Holtek Semiconductor 

PATENTED

HT1647A

Buzzer Tone Output

A simple tone generator is implemented in the

HT1647A. The tone generator can output a pair of differ-

ential driving signals on the BZ and BZ which are used

to generate a single tone.

By executing the TONE 4K and TONE 2K commands

there are two tone frequency outputs selectable that can

turn on the tone output. The TONE 4K and TONE 2K

commands set the tone frequency to 4kHz and 2kHz, re-

spectively. The tone output can be turned off by invoking

the TONE OFF command. The tone outputs, namely BZ

and BZ, are a pair of differential driving outputs used to

drive a piezo buzzer. Once the system is disabled or the

tone output is inhibited, the BZ and the BZ outputs will

remain at low level.

Name Command Code

Function

TONE

OFF

X100-0000-1000-XXXX Turn-off tone output

TONE

4K

Turn-on tone output,

X100-0001-0000-XXXX tone frequency is

4kHz

TONE

2K

Turn-on tone output,

X100-0001-0001-XXXX tone frequency is

2kHz

Buzzer Tone Output Command Code

Command Format

The HT1647A can be configured by software setting.

There are two mode commands to configure the

HT1647A resource and to transfer the LCD display data.

The configuration mode of the HT1647A is called com-

mand mode, and its command mode ID is 100. The

command mode consists of a system configuration

command, a system frequency selection command, an

LCD configuration command, a tone frequency selec-

VLCD

4V

4V

Bias

1/5

1/4

Large Bias Current

300mA

375mA

tion command, a bias current selection command, a

gray scale level selection command, a timer/WDT set-

ting command, and an operating command. The data

mode, on the other hand, includes READ, WRITE, and

READ-MODIFY-WRITE operations.

The following are the data mode ID and the command

mode ID:

Operation

Mode

ID

READ

Data

110

WRITE

Data

101

READ-MODIFY-WRITE

Data

101

COMMAND

Command 100

If successive commands have been issued, the com-

mand mode ID can be omitted. While the system is op-

erating in the non-successive command or the

non-successive address data mode, the CS pin should

be set to ²1² and the previous operation mode will also

be reset. The CS pin returns to ²0², so a new operation

mode ID should be issued first.

Bias Generator

The HT1647A bias voltage belongs to internal resistor

type. It provides two kinds of bias option named 1/5 bias

and 1/4 bias respectively. It is recommended to select

1/5 bias to fit TN-type, STN-type LCDs and select 1/4

bias to fit ECB-type LCDs. It also provides three kinds of

bias current option by programming to suitably drive an

LCD panel. The three kinds of bias current are large,

middle, and small, respectively. Usually, large panel

LCD can be excellently displayed by large bias current.

Relatively, it consumes large current when LCD ON

command is used. Small bias current provides low

power consumption during On condition when the LCD

is normally displayed. The following are the reference

value table.

Middle Bias Current

100mA

125mA

Small Bias Current

40mA

50mA

Rev. 1.40

12

April 29, 2011

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