HT1621
OFF command turns the LCD display off by dis-
abling 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. Using the LCD related commands,
the HT1621 can be compatible with most types
of LCD panels.
Command format
The HT1621 can be configured by the S/W set-
ting. There are two mode commands to configure
the HT1621 resources and to transfer the LCD
display data. The configuration mode of the
HT1621 is called command mode, and its com-
mand mode ID is
1 0 0.
The command mode con-
sists of a system configuration command, a
system frequency selection command, a LCD con-
figuration 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 follow-
ing are the data mode IDs and the command
mode ID:
Operation
READ
WRITE
READ-MODIFY-WRITE
COMMAND
Mode
Data
Data
Data
ID
110
101
101
the system is operating in the non-successive
command or the non-successive address data
mode, the CS pin should be set to "1" and the
previous operation mode will be reset also.
Once the CS pin returns to "0" a new operation
mode ID should be issued first.
Interfacing
Only four lines are required to interface with
the HT1621. The CS line is used to initialize the
serial interface circuit and to terminate the com-
munication between the host controller and the
HT1621. If the CS pin is set to 1, the data and
command issued between the host controller and
the HT1621 are first disabled and then initial-
ized. Before issuing a mode command or mode
switching, a high level pulse is required to initial-
ize the serial interface of the HT1621. The DATA
line is the serial data input/output line. Data to
be read or written or commands to be written
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 sig-
nal, 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 interval
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 HT1621 on the
rising edge of the WR signal. There is an optional
IRQ line to be used as an interface between the
host controller and the HT1621. The IRQ pin can
be selected as a timer output or a WDT overflow
flag output by the S/W setting. The host control-
ler can perform the time base or the WDT func-
tion by being connected with the IRQ pin of the
HT1621.
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, namely
1 0 0,
can be omitted. While
12
January 10, 2001
ETC [ ETC ]
