PATENTED
HT1620
Interfacing
The bold form of 1 0 0, namely 1 0 0, 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.
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.
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 1 0 0. 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
Data
ID
READ
1 1 0
1 0 1
1 0 1
1 0 0
WRITE
Data
READ-MODIFY-WRITE
COMMAND
Data
Command
The mode command should be issued before the data or
command is transferred. If successive commands have
been issued, the command mode ID, 1 0 0, 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.
Rev. 1.80
9
July 27, 2009
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
