HD44780U Datasheet, PDF (33/59 Pages) Hitachi Semiconductor – Dot Matrix Liquid Crystal Display Controller/Driver

$* '.!"^HD44780U
• Interfacing to a 4-bit MPU
The HD44780U can be connected to the I/O port of a 4-bit MPU. If the I/O port has enough bits, 8-bit
data can be transferred. Otherwise, one data transfer must be made in two operations for 4-bit data. In
this case, the timing sequence becomes somewhat complex. (See Figure 17.)
See Figure 18 for an interface example to the HMCS4019R.
Note that two cycles are needed for the busy flag check as well as for the data transfer. The 4-bit
operation is selected by the program.
RS
R/W
E
Internal
operation
DB7
Functioning
IR7 IR3
Instruction
write
Busy AC3
Busy flag
check
Not
busy AC3
Busy flag
check
D7 D3
Instruction
write
Note: IR7 , IR3 are the 7th and 3rd bits of the instruction.
AC3 is the 3rd bit of the address counter.
Figure 17 Example of 4-Bit Data Transfer Timing Sequence
HMCS4019R
HD44780
D15
RS
COM1 to ¹⁶
D14
R/W
COM16
D13
E
LCD
R10 to R13
4
DB4
to
DB7
SEG1 to
SEG40
40
Figure 18 Example of Interface to HMCS4019R
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