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Basic information Dot matrix charaterr LCD
The infromation in this document is a HD44780-Based LCD Modules compatible.
The general Dot matrix character LCD has 14 pins as following.
| Pin Number |
Symbol |
| 1 |
Gnd |
| 2 |
Vcc |
| 3 |
Vo |
| 4 |
RS |
| 5 |
R/W |
| 6 |
E |
| 7 |
DB0 |
| 8 |
DB1 |
| 9 |
DB2 |
| 10 |
DB3 |
| 11 |
DB4 |
| 12 |
DB5 |
| 13 |
DB6 |
| 14 |
DB7 |
|
|
|
| Signal name |
No. of
Lines |
I/O |
Connected
to |
Function |
| DB4-DB7 |
4 |
I/O |
CPU |
4 lines of high order data bus. Bi-directional transfer of data
between MPU and module is done through these lines. Also DB7
can be used as a busy flag. These lines are used as data in 4 bit
operation |
| DB0-DB3 |
4 |
I/O |
CPU |
4 lines of low order data bus. Bi-directional transfer of data
between MPU and module is done through these lines. In 4 bit
operation, these are not used and should be grounded. |
| E |
1 |
I |
CPU |
Enable - Operation start signal for data read/write. |
| R/W |
1 |
I |
CPU |
Signal to select Read or Write
“0”: Write
“1”: Read |
| RS |
1 |
I |
CPU |
Register Select
“0”: Instruction register (Write)
: Busy flag; Address counter (Read)
“1”: Data register (Write, Read) |
| Vo |
1 |
- |
Power Supply |
Terminal for LCD drive power source or use for dimming. |
| Vcc |
1 |
- |
Power Supply |
+5Vdc |
| Gnd |
1 |
- |
Power Supply |
Groung |
|
HD44780 instruction set
| Instruction |
Code |
Description |
Execution time** |
| RS |
R/W |
DB7 |
DB6 |
DB5 |
DB4 |
DB3 |
DB2 |
DB1 |
DB0 |
| Clear display |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
Clears display and returns cursor to the home position (address 0). |
1.64mS |
| Cursor home |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
* |
Returns cursor to home position (address 0). Also returns display being shifted to the original position. DDRAM contents remains unchanged. |
1.64mS |
| Entry mode set |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
I/D |
S |
Sets cursor move direction (I/D), specifies to shift the display (S). These operations are performed during data read/write. |
40uS |
| Display On/Off control |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
D |
C |
B |
Sets On/Off of all display (D), cursor On/Off (C) and blink of cursor position character (B). |
40uS |
| Cursor/display shift |
0 |
0 |
0 |
0 |
0 |
1 |
S/C |
R/L |
* |
* |
Sets cursor-move or display-shift (S/C), shift direction (R/L). DDRAM contents remains unchanged. |
40uS |
| Function set |
0 |
0 |
0 |
0 |
1 |
DL |
N |
F |
* |
* |
Sets interface data length (DL), number of display line (N) and character font(F). |
40uS |
| Set CGRAM address |
0 |
0 |
0 |
1 |
CGRAM address |
Sets the CGRAM address. CGRAM data is sent and received after this setting. |
40uS |
| Set DDRAM address |
0 |
0 |
1 |
DDRAM address |
Sets the DDRAM address. DDRAM data is sent and received after this setting. |
40uS |
| Read busy-flag and address counter |
0 |
1 |
BF |
CGRAM / DDRAM address |
Reads Busy-flag (BF) indicating internal operation is being performed and reads CGRAM or DDRAM address counter contents (depending on previous instruction). |
0uS |
| Write to CGRAM or DDRAM |
1 |
0 |
write data |
Writes data to CGRAM or DDRAM. |
40uS |
| Read from CGRAM or DDRAM |
1 |
1 |
read data |
Reads data from CGRAM or DDRAM. |
40uS |
Bit names
| Bit name |
Setting / Status |
| I/D |
0 = Decrement cursor position |
1 = Increment cursor position |
| S |
0 = No display shift |
1 = Display shift |
| D |
0 = Display off |
1 = Display on |
| C |
0 = Cursor off |
1 = Cursor on |
| B |
0 = Cursor blink off |
1 = Cursor blink on |
| S/C |
0 = Move cursor |
1 = Shift display |
| R/L |
0 = Shift left |
1 = Shift right |
| DL |
0 = 4-bit interface |
1 = 8-bit interface |
| N |
0 = 1/8 or 1/11 Duty (1 line) |
1 = 1/16 Duty (2 lines) |
| F |
0 = 5x7 dots |
1 = 5x10 dots |
| BF |
0 = Can accept instruction |
1 = Internal operation in progress |
DDRAM address for a 1-line LCD (N=0)
| Display size |
Visible |
| Character positions |
DDRAM addresses |
| 1*8 |
00..07 |
0x00..0x07 |
| 1*16 |
00..15 |
0x00..0x0F |
| 1*20 |
00..19 |
0x00..0x13 |
| 1*24 |
00..23 |
0x00..0x17 |
| 1*32 |
00..31 |
0x00..0x1F |
| 1*40 |
00..39 |
0x00..0x27 |
DDRAM address for a 2-line LCD (N=1)
| Display size |
Visible |
| Character positions |
DDRAM addresses |
| 2*16 |
00..15 |
0x00..0x0F + 0x40..0x4F |
| 2*20 |
00..19 |
0x00..0x13 + 0x40..0x53 |
| 2*24 |
00..23 |
0x00..0x17 + 0x40..0x57 |
| 2*32 |
00..31 |
0x00..0x1F + 0x40..0x5F |
| 2*40 |
00..39 |
0x00..0x27 + 0x40..0x67 |
DDRAM address for a 4-line LCD(N=1)
| Display size |
Visible |
| Character positions |
DDRAM addresses |
| 4*16 |
00..15 |
0x00..0x0F + 0x40..0x4F + 0x14..0x23 + 0x54..0x63 |
| 4*20 |
00..19 |
0x00..0x13 + 0x40..0x53 + 0x14..0x27 + 0x54..0x67 |
| 4*40 |
(00..39) on first and
(00..39) on second controller |
(0x00..0x27 + 0x40..0x67) for first controller
(0x00..0x27 + 0x40..0x67) for second controller |
Interfacing to MCU
The LCD has 2 mode to interface with microcontroller are 4-bit interface and 8-bit interface
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 18.)
See Figure 19 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
Interfacing to an 8-bit MPU
See Figure 17 for an example of using a I/O port (for a single-chip microcomputer) as an interface
device.
In this example, P30 to P37 are connected to the data bus DB0 to DB7, and P75 to P77 are connected
to E, R/:, and RS, respectively.
Initializing by Instruction
8-bit interface
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