LCD Commands

Notes:

• DDRAM = Display Data RAM.
• CGRAM = Character Generator RAM.
• DDRAM address corresponds to cursor position.
• Address Counter is used for both DDRAM and CGRAM.
• * = Don't care.
• ** = Based on Fosc = 250KHz.

Bit names

Bit	Settings
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

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   0   0   0   0   0   0   1 

Details
Writes space code (20h) into all DD RAM addresses. Sets address counter to DD RAM location 0. Returns display to its original state if it was shifted. In other words, the display disappears and the cursor or blink goes to the left edge of the display (the first line if 2 lines are displayed). Sets entry mode I/D to 1 (Increment Mode). Entry mode shift (S) bit remains unchanged.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
 0   0   0   0   0   0   0   0   1   * 

Details
Sets the address counter to DD RAM location 0 in the address counter. Returns display to its original state if it was shifted. DD RAM contents remain unchanged. The cursor or blink goes to the left edge of the display (the first line if 2 lines are displayed).

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   0   0   0   0   1  I/D  S 

Details
Specifies whether to increment (I/D = 1) or decrement (I/D = 0) the address counter after subsequent DD RAM read or write operations.

If S = 1 the display will be shifted to the left (if I/D = 1) or right (if I/D = 0) on subsequent DD RAM write operations. This makes it looks as if the cursor stands still and the display moves when each character is written to the DD RAM. if S = 0 the display will not shift on subsequent DD RAM write operations.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   0   0   0   1   D   C   B 

Details
D: The display is ON when D = 1 and OFF when D = 0. The DD RAM contents remain unchanged.

C: The cursor is displayed when C = 1 and is not displayed when C = 0.
The cursor is displayed as 5 dots in the 8th line when the 5 x 7 dot character font is selected and as 5 dots in the 11th line when the 5 x 10 dot character font is selected.

B: The character at the the cursor position blinks when B = 1.
Blinking is performed by switching between all blank dots and the display character every 409.6 ms.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   0   0   1  S/C R/L  *   * 

Details
Shifts cursor position or display to the right or left without writing or reading display data. This function is used to correct or search for the display. In a 2-line display, the cursor moves to the 2nd line when it passes the 40th digit of the 1st line. Notice that the 1st and 2nd line displays will shift at the same time. When the displayed data is shifted repeatedly each line only moves horizontally. The 2nd line of the display does not shift into the 1st line position.

S/C R/L                                          
=== ===                                          
 0   0   Shifts the cursor position to the left 
         (Address Counter is decremented by 1)   
 0   1   Shifts the cursor position to the right
         (Address Counter is incremented by 1)  
 1   0   Shifts the entire display to the left  
         The cursor follows the display shift   
 1   1   Shifts the entire display to the right 
         The cursor follows the display shift   

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   0   1   DL  N   F   *   * 

Details
This command should be issued only after automatic power-on initialization has occurred, or as part of the module initialization sequence.
DL: Sets interface data length

Data sent or received in 8 bit lengths (DB7-DB0) when DL = 1

Data sent or received in 4 bit lengths (DB7-DB4) when DL = 0

When the 4 bit length is selected, data must be sent or received in pairs of 4-bits each. The most-significant 4 bits are sent or received first.

F: Sets character font

    display Character  Duty                             
N F  lines    Font    Factor Remarks                    
=== ======= ========= ====== =======                    
0 0    1    5x 7 dots  1/8    -                         
0 1    1    5x10 dots  1/11   -                         
1 *    2    5x 7 dots  1/16  Cannot display 2 lines with
                             5x10 dot character font    

Note that a 1 line x 16 character display is treated as a 2 line x 8 character display. The first `line' is the left eight character positions on the display and the second `line' is the right eight character positions. This also means that the 16 characters on the display do not occupy 16 sequential DD RAM locations.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   0   1   A   A   A   A   A   A 

Details
Sets the specified value (AAAAAA) into the address counter. Subsequent read or write operations transfer data from, or to, the character generator RAM.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   0   1   A   A   A   A   A   A   A 

Details
Sets the specified value (AAAAAAA) into the address counter. Subsequent read or write operations transfer data from, or to, the display RAM. Note: Adjacent display RAM locations do not necessarily refer to adjacent display positions.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 0   1   BF  A   A   A   A   A   A   A 

Details
Reads the busy flag (BF) that indicates the state of the LCD module. BF = 1 indicates that the module is busy processing the previous command. BF = 0 indicates that the module is ready to perform another command.

The value of the address counter is also returned. The same address counter is used for both CG and DD RAM transfers.

This command can be issued at any time. It is the only command which the LCD module will accept while a previous command is still being processed.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 1   0   D   D   D   D   D   D   D   D 

Details
Writes a byte (DDDDDDDD) to the CG or the DD RAM. The destination (CG RAM or DD RAM) is determined by the most recent `Set RAM Address' command. The location to which the byte will be written is the current value of the address counter. After the byte is written the address counter is automatically incremented or decremented according to the entry mode. The entry mode also determines whether or not the display will shift.

RS  R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
=== === === === === === === === === ===
 1   1   D   D   D   D   D   D   D   D 

Details
Reads a byte (DDDDDDDD) from the CG or DD RAM. The source (CG RAM or DD RAM) is determined by the most recent `Set RAM Address' command. The location from which the byte will be read is the current value of the address counter. After the byte is reda the address counter is automatically incremented or decremented according to the entry mode.