HT1647 datasheet(10/17 Pages) HOLTEK

10 / 17 page

HT1647

Rev. 1.40

November 9, 2010

PATENTED

Time Base and Watchdog Timer

- WDT

The time base generator and WDT share the same

counter which is divided by 256. The IRQ clock can be pro-

grammed as 1Hz, 2Hz, ...., 128Hz output. TIMER

DIS/EN/CLR, WDT DIS/EN/CLR and IRQ EN/DIS are in-

dependent from each other. Once the WDT time-out oc-

curs, the IRQ pin will remain at a logic low level until the

CLR WDT or the IRQ DIS command is issued.

If an external clock is selected as the system frequency

source, the SYS DIS command turns out invalid and the

power down mode fails to be carried out until the exter-

nal clock source is removed.

Buzzer Tone Output

A simple tone generator is implemented in the HT1647.

The tone generator can output a pair of differential driv-

ing 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.

Command Format

The HT1647 can be configured by software setting.

There are two mode commands to configure the

HT1647 resource and to transfer the LCD display data.

The configuration mode of the HT1647 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-

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

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.

W D T E N / D I S

I R Q E N / D I S

C K

C L R W D T

C l o c k S o u r c e

/ 4

/ 2 5 6

T i m e B a s e

C L R T i m e r

I R Q

W D T

V D D

T I M E R E N / D I S

Time Base and WDT Configurations

Name

Command Code

Function

TONE OFF

X100-0000-1000-XXXX

Turn-off tone output

TONE 4K

X100-0001-0000-XXXX

Turn-on tone output, tone frequency is 4kHz

TONE 2K

X100-0001-0001-XXXX

Turn-on tone output, tone frequency is 2kHz

Buzzer Tone Output Command Code

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