HT1620

Rev. 1.80

9

July 27, 2009

PATENTED

The bold form of 1 0 0, namely 100, indicates the com-

mand mode ID. If successive commands have been is-

sued, the command mode ID will be omitted, except for

the first command. The LCD OFF command turns the

LCD display off by disabling the LCD bias generator.

The LCD ON command, on the other hand, turns the

LCD display on by enabling the LCD bias generator. The

BIAS and COM are the LCD panel related commands.

With the use of the LCD related commands, the HT1620

can be compatible with most types of LCD panels.

Command Format

The HT1620 can be configured by the S/W setting. There

are two mode commands to configure the HT1620 re-

sources and to transfer the LCD display data. The configu-

ration mode of the HT1620 is called command mode, and

its command mode ID is 100. The command mode con-

sists of a system configuration command, a system fre-

quency selection command, an LCD configuration

command, a tone frequency selection command, a

timer/WDT setting command, and an operating command.

The data mode, on the other hand, includes READ,

WRITE, and READ-MODIFY-WRITE operations. The fol-

lowing are the data mode IDs and the command mode ID:

Operation

Mode

ID

READ

Data

1 1 0

WRITE

Data

1 0 1

READ-MODIFY-WRITE

Data

1 0 1

COMMAND

Command

1 0 0

The mode command should be issued before the data or

command is transferred. If successive commands have

been issued, the command mode ID, 100, can be omit-

ted. While the system is operating in the non-successive

command or the non-successive address data mode,

the CS pin should be set to

²1² and the previous opera-

tion mode will be reset also. Once the CS pin returns to

²0², a new operation mode ID should be issued first.

Interfacing

Only four lines are required to interface with the

HT1620. The CS line is used to initialize the serial inter-

face circuit and to terminate the communication between

the host controller and the HT1620. If the CS pin is set to

1, the data and command issued between the host con-

troller and the HT1620 are first disabled and then initial-

ized. Before issuing a mode command or mode switching,

a high level pulse is required to initialize the serial interface

of the HT1620. The DATA line is the serial data input/out-

put line. Data to be read or written or commands to be writ-

ten have to be passed through the DATA line. The RD line

is the READ clock input. Data in the RAM are clocked out

on the falling edge of the RD signal, and the clocked out

data will then appear on the DATA line. It is recommended

that the host controller read in correct data during the in-

terval between the rising edge and the next falling edge of

the RD signal. The WR line is the WRITE clock input. The

data, address, and command on the DATA line are all

clocked into the HT1620 on the rising edge of the WR sig-

nal. There is an optional IRQ line to be used as an inter-

face between the host controller and the HT1620. The

IRQ pin can be selected as a timer output or a WDT over-

flow flag output by the S/W setting. The host controller can

perform the time base or the WDT function by connecting

with the IRQ pin of the HT1620.