DISPLAYING CUSTOMIZED CHARACTER USING CGROM IN LCD DISPLAY LM016L

DISPLAYING CUSTOMIZED CHARACTER USING CGROM IN LCD DISPLAY LM016L

CGROM – Character Generator ROM

In LCD display we have seen that, when we send ASCII value it directly display.

Actually the CGROM has all ASCII value store in it. So when we send any ASCII value it compare it with CGROM and displays it.

A user defined Character Patterns can also be generated using mask-programmed ROM.

To Generate a Customized Character like Symbol, smiley etc.

We use 5x8 dot matrix to generate a symbol.

	Don’t Care			5 COLUMN					Hex value
8  R O W	0	0	0	0	X	X	X	0	0x0E
	0	0	0	X	X	X	X	X	0x1F
	0	0	0	X	0	0	0	X	0x11
	0	0	0	X	0	0	0	X	0x11
	0	0	0	X	0	0	0	X	0x11
	0	0	0	X	0	0	0	X	0x11
	0	0	0	X	X	X	X	X	0x1F
	0	0	0	X	X	X	X	X	0x1F

X= 1;

0 = 0;

Higher 3-bit are don’t care because the data send is 8bit

So we use addition 3-bits a predefined 0 and rest of 5 bit are the 5 columns and 8 row are used to defined each row and column in the display.

X indicates that the bit is 1.

0 indicates the bit as 0.

In 5x8 matrix only the higher 3 bit are don’t care.

The symbol Created is a Battery symbol. We can generator many type of symbol using mask-programmed ROM (CGROM location that are unused)

The Hex value created for symbol must be place in CGROM location 40H.

The 40H memory has 8 addressable location from 00 to 07.

And while displaying we should mention addressable location of 40H that are storing 8-byte data in each location from 0x00 to 0x07.

Each location i.e. 0x00 hold 8-byte data. 

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INTERFACING OF LCD DISPLAY TO MICRO-CONTROLLER 8051

INTERFACING OF LCD DISPLAY TO MICRO-CONTROLLER MC8051

The LCD used here is LM016L and Micro-controller is 8051(P89V51RD2).

It is 16 pin Lcd display in which 3 pin are dedicated as control pin and 8 pin for data transfer.

Here I had Connected the Port 0 of MC to LCD and P2(0,1,2) pin to control pin of LCD.

NOTE: 3 control pins are RS = Register Select, RW = Read/Write, and E = Enable.

The working of LCD main depends on this 3 control pin:

• When RS = 0, Means Register selected is Command register and the data send are command for LCD.
• When RS = 1, Means Register Selected is Data register and the data is directly send to DDRAM (Display Data RAM) for displaying the String.
• RW pin is Read or Write enable pin. RW = 0, Means Write functions is select so that we can write data or command into LCD RAM.
• RW pin when is set as 1, means Read function is selected. We only read the status of LCD DDRAM, i.e. whether it’s Busy or ready to accept the data.
• E = Enable pin is used to latch the data send from Micro-controller to LCD.
• When E get high to low pulse it latch the data into LCD RAM.
• So for every data or command to be send to LCD display the E pin must have high to low pulse.

Important Command of LCD:

• Clear the display = 0x01;
• Display on and cursor blinking = 0x0E;
• Display on and cursor blinking off = 0x0C;
• Cursor incrementing = 0x06;
• 1^st location in the 1^st line of lcd display = 0x80;
• 1^st location in the 2^nd line of lcd display = 0xC0;
• For Left Shifting the data of lcd = 0x18;
• For Right shifting the data of lcd = 0x1C;

In this method I have used the pointer to send of number string

This method is called as pass by Reference.

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For Video on this example: Click on this link for video