HT1620
Name
LCD OFF
LCD ON
Command Code
1 0 0 0 0 0 0 0 0 1 0 X
1 0 0 0 0 0 0 0 0 1 1 X
Function
Turn off LCD outputs
Turn on LCD outputs
c=0: 1/2 bias option
c=1: 1/3 bias option
BIAS and COM 1 0 0 0 0 1 0 a b X c X
ab=00: 2 commons option
ab=01: 3 commons option
ab=10: 4 commons option
Command format
Interfacing
The HT1620 can be configured by the S/W set-
ting. There are two mode commands to configure
the HT1620 resources and to transfer the LCD
display data. The configuration mode of the
HT1620 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, an LCD
configuration command, a tone frequency selec-
tion 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:
Only four lines are required to interface with
the HT1620. The CS line is used to initialize the
serial interface circuit and to terminate the com-
munication between the host controller and the
HT1620. If the CS pin is set to 1, the data and
command issued between the host controller 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 initial-
ize the serial interface of the HT1620. 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 HT1620 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 HT1620. 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 connecting with the IRQ pin of the
HT1620.
Operation
Mode
Data
Data
Data
ID
READ
1 1 0
1 0 1
1 0 1
WRITE
READ-MODIFY-WRITE
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, 1 0 0, can be omitted. While the sys-
tem is operating in the non-successive com-
mand or the non-successive address data mode,
the CS pin should be set to ²1² and the previous
operation mode will be reset also. Once the CS
pin returns to ²0², a new operation mode ID
should be issued first.
10
July 26, 1999
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
