LCD INTERFACING

-


LCD INTERFACING
8.1 LCD Features
LCD stands for Liquid Crystal Display are the most widely used output devices for 89c51 type microcontroller. Nowadays LCDs is finding widespread use compared to LEDs and 7-segment. This is due to following specific features:
1. The declining prices of LCDs make its use cost-effective.
2. The ability to display numbers, characters and graphics. This is contrast to LEDs, which has limited to numbers and few characters. Incorporation of a refreshing controller into LCD, thereby relieving the CPU of the task of refreshing the LCD. In contrast, the LED must be refreshed by the CPU to keep displaying data.


3. Ease of programming for characters and graphics.
8.2  LCD Pin Descriptions


The LCD which we have used in our TRAINER KIT is discussed in this section. It has 14 pins. Figure shows the position of various pins.

1. VCC, VSS, and VEE
While VCC and VSS provide +5V and ground, respectively, VEE is used for controlling LCD contrast.

2. RS (Register Select)
There are two very important registers inside the LCD. The RS pin is used for their selection as follows. If RS=0, the instruction command code register is selected, allowing the user to send a command such as clear display, cursor at home, etc. If RS=1, the data register is selected, allowing the user to send data to be displayed on LCD.

3. R/W (Read/Write)
R/W input allows the user to write information to LCD or read information from it. R/W=1 when reading; R/W=0 when writing.

4. E (Enable)
The enable pin is used by the LCD to latch information presented to its data pins. When data is supplied to data pins, a high-to-low pulse must be applied to this pin in order for the LCD to latch in the data present the data pins. This pulse must be a minimum of 450 ns wide.

5. D0-D7 (8-bit Data bus)
The 8-bit data pins, D0-D7, are used to send information to the LCD or read the contents of the LCD’s internal registers. To display letters and numbers, we send ASCII codes for the letters A-Z, a-z, and numbers 0-9 to these pins while making RS=1. There are also instruction command codes that can be sent to LCD to clear the cursor to the home position or blink the cursor. Table lists some of the instruction command codes.

8.3 Connection of LCD with 8255
The main purpose of LCD in our Trainer kit is to display the name of the practical which is going to perform by the user and so LCD is programmed according. Figure shows various connections required to interface an LCD to 89c51. Here data lines of LCD are connected to 8 port of 89c51 microcontroller.








Interfacing of LCD to Microcontroller
 On this data lines, various command codes for LCD settings and data codes which are required to display are sent. There are three controlling lines for LCD viz, RS, R/W and E. RS that is register select is connected to designated port pin of 89c51 and set or reset as required. Similarly remaining two lines R/W that is Read/Write and E that is Enable are connected to designated 89c51 port pins and set or reset as required.


 

Comments

Post a Comment

Popular posts from this blog

AUDIO SPOTLIGHTING

-
Image
INTRODUCTION n   Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By ‘shining’ sound to one location, specific listeners can be targeted with sound without others nearby hearing it, ie to focus sound into a coherent and highly directional beam. It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any conventional loud speaker. n   The Audio Spotlight & Hyper Sonic Sound Technology (developed by American Technology Corporation), uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light. Audio spotlighting exploits the property of non-linearity of air. When inaudible ultrasound pulses are fired into the air, it spontaneously converts the inaudible ultrasound into audible sound tones, hence proved that as with water, sound propagation in air is just as non-linear, and can be calcul...
Read more

INTERFACING OF EEPROM with 8051

-
Image
7.1 Introduction As we know, ROM is a memory that does not lost its contents when the power is turned off. For this reason ROM is also called Non-Volatile Memory. There are different types of ROM such as PROM, EPROM, EEPROM, Flash EPROM and Mask ROM. In which PROM refers to the Kind of ROM that the user can burn information into. PROM is a user programmable memory. PROM is referred to as OTP (One time programmable). EPROM was invented to allow making changes in the contents of PROM after it is burned. In short, one can program the memory chip and erase it thousands of time. This is especially necessary during development of microcontroller based project. EEPROM is electrically erasable programmable ROM. EEPROM has several advantages over EPROM. EEPROM does not require external eraser and programming device. Flash EPROM has become a popular user programmable memory chip. The reason behind that is the eraser of entire content takes less than a second that why it is named Flash memory. Wh...
Read more

making a Lan wire

-
Image
Image one is crimping tool; second and third is RJ-45 connector and fourth is peeled lan cable... Cables are generally of two categories,, 1)CAT-5 2)CAT-6 former belong to the category of UTP( unshielded twisted pair ) and later to STP also the EIA/TIA(electronic industry alliance or association and telecom industry alliance) has maintained two standards 568-A and 568-B.. When u peel off the jacket of the lan cable you will get eight types of wires in a pair of four ..these are: 1)white with orange stripes(call it white of orange or W/O) 2)Orange 3)white of green 4)blue 5)white of blue 6)green 7)white of brown 8) brown also at both the ends of lan cable we have two connectors .. These are RJ-45 connectors... always hold connectors with knob side downward..And when we place the wires in the above mentioned fashion in the RJ-45 connector it is 568-B standard.. EIA/TIA has defined three categories of cables... 1)straight cables 2...
Read more