
AN.No.G121600N000-3D0E
- 9 -
In order to read the content of the output register, the Chip Select must be selected, D/I must be
1, and R/W must be 1. When executing the “Read” instruction, the contents of the output
register stored at that time are output during the time that “E” is 1. When “E” falls, display data
of the currently indicated address is written in the output register. After that, the address
advances by one.
The contents of the output register are rewritten by the Read instruction. The data is retained
by the address set or other instructions. Accordingly, when performing the address set, and next
executing the Read instruction, the data of the specified address is not output and the data of
the address which is specified is output at the second data read time. Therefore, when setting
the address, a dummy read is needed once. See Figure 4.
Busy
Check
Data Read
(dummy)
Address
Set
(Address
N)
N+1 address data
N+2
N
N+1
N address data
D / I
R/W
E
Address
Output Register
DB
0
to DB
7
Busy
Check
Busy
Check
Data Read
(N address
data)
Busy
Check
Data Read
(N+1 address
data)
Figure 4 Read Timing
(2)
Busy flag
The status when busy flag is “1” means that the module is operating internally. Instructions
other than he Status Read are not available at this time. The busy flag is output to DB
7
by the
Status Read instruction. Ensure that the busy flag is “0” before executing the instruction.
BUSY
E
T
BUSY
F
is frequency of
1
or
2
(1 / 2 the source oscillation frequency of HD61203): 215 kHz typ.
1
F
T
BUSY
3
F
Figure 5 Busy Flag
(3)
Display ON/OFF Flip/Flop
The display ON/OFF Flip/Flop is a flip-flop function that determines whether the display data
corresponding to the RAM data is output to the segment on the LCD (ON status ) or goes to all
nonlit status regardless of the RAM data (OFF status). This is controlled by the display ON/OFF
instruction. When the RST signal becomes “0,” the display goes to OFF status. This flip-flop
status is output to DB
5
by the Status Read instruction.
Even when performing display ON/OFF, the data inside the RAM is not affected.