2. 4-Bit Data Transfer with a Single-Line, 16-Char-
acter Display (Using Internal Reset). Table 14
shows a sample operating procedure for an LCD
unit in this mode. After power has been turned
on, the 8-bit data transfer mode is in effect, and
the first write operation is assumed to be an 8-bit
data transfer.
Since the data lines DB
0
- DB
3
are not con-
nected, this data is not accepted and must be
written again (i.e. the function set instruction
must be written twice). Subsequent data trans-
fers are completed in two 4-bit transfer opera-
tions (see Table 14).
RS
R/W
E
OPERATING
STATUS
DB
7
INTERNAL OPERATION READY FOR DATA
IR
7
BUSY
NOT
BUSY
IR
3
AC
3
AC
3
D
7
D
3
LCD27-32
Write Instruction
NOTE: IR
7
, IR
3
: Instruction bits 7 and 3.
AC
3
: Address counter bit 3.
Write InstructionCheck Busy Flag Check Busy Flag
Figure 9. 4-Bit Interface Timing (Example)
O
1
SM200
4
LCD UNIT
LCD27-33
O
3
O
2
P
10
- P
13
RS
E
R/W
DB
4
- DB
7
Figure 10. Connection to SM200
Dot-Matrix LCD Units
Display Unit User’s Manual 23
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