lcd commands and understanding of LCD module

• Basic unit of display is pixel.
• PIXEL= picture + element.

• Above figure shows that each LCD have its own pixel rows and columns like 1×16 has single raw and sixteen columns i.e. 16 pixel and each pixel size is of 5×8 as shown but we can see only 5×7 cause last raw is used by cursor.
• Each character is display according to these pixels size.

• Below pic shows block diagram of 16×2 LCD.

• Rs -> Register select

Rs=1 mean data register is selected.

Rs=0 mean command register is selected.

• RW -> Read/Write

RW=1 mean reading from LCD module.

RW=0 mean writing to LCD module.

• EN -> Enable

EN= high to low ( Logic ‘1’ delay Logic ‘0’ ) for use LCD module .

• How characters are generate on LCD screen?

   

•  There are three memories in LCD to manipulate display characters:

1. CGROM – character generating ROM which is responsible for stored standard character pattern.
2. CGRAM – character generating RAM which holds custom character pattern space ( total 8 in 2×16 module).
3. DDRAM – data display RAM which stores ASCII codes.

• Steps to understand how character display:

1. Control unit of LCD receives signal(basically it is ASCII code) from user and ask to DDRAM for its match.
2. If ASCII code match, control unit maps corresponding character pattern from CGROM.
3. According to that character pattern,  LCD screen energies and we can see character on it .

• 16×2 lcd commands

 

Code (Hex)	working of lcd commands
1	Clear display screen
2	Return home
4	Decrement cursor (shift cursor to left)
6	Increment cursor (shift cursor to right)
5	Shift display right
7	Shift display left
8	Display off, cursor off
A	Display off, cursor on
C	Display on, cursor off
E	Display on, cursor blinking
F	Display on, cursor blinking
10	Shift cursor position to left
14	Shift cursor position to right
18	Shift the entire display to the left
1C	Shift the entire display to the right
80	Force cursor to beginning to 1st line
C0	Force cursor to beginning to 2nd line
90	Force cursor to beginning to 3rd line
D0	Force cursor to beginning to 4th line
38	2 lines and 5×7 matrix (8-bit mode)
28	2 lines and 5×7 matrix (4-bit mode)
n	Next line
t	Tab
r	enter