30-08-2014, 01:06 PM
MOVING MESSAGE DISPLAY SYSTEM
[attachment=67438]
Introduction
LCD-based moving-message displays are becoming popular for transmitting information to large groups of people quickly. These can be used indoors or outdoors. We can find such displays in areas like railway platforms, banks, public offices, hotels, training institutes, nightclubs and shops.
The objective of the projects is to provide non-commercial and purely academic insight into microcontroller assembly programming. The over all goal of the projects is to provide connectivity between microcontroller and a HD44780 compatible LCD.
The LCD comes with a 14pin interface, which includes pins to receive power supply and ground as well. These 14pins have to be interfaced with microcontroller output ports to send instructions, which initialize the LCD in appropriate modes, and also to send data from the microcontroller is intended for display on the LCD output screen.
A string or message can be displayed on LCD by sending its characters to data register after configuring the command register of LCD. To create dynamic effects, a specific command instruction is sent to LCD via microcontroller AT89C51.
Moving message on LCD are ideal for all type of commercial establishments like Hotels, Restaurants, Retail Shops Banks, Airports, Clinics, Hospitals and other such places to get maximum attention of people. These displays attract customers to watch the display with curiosity and your scrolling message also is conveyed simultaneously.
BASIC PINS
PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller’s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)
PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only connect a crystal at these pins to provide clock pulses to the circuit.
PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V 500mA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.
PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If external memory is connected then PIN 31, also called EA/VPP, should be connected to ground to indicate the presence of external memory. PIN 30 is called ALE (address latch enable), which is used when multiple memory chips are connected to the controller and only one of them needs to be selected.We will deal with this in depth in the later chapters. PIN 29 is called PSEN. This is "program store enable". In order to use the external memory it is required to provide the low voltage (0) on both PSEN and EA pins.
PORTS
There are 4 8-bit ports: P0, P1, P2 and P3.
PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or additional functions associated with them based upon the context of their usage.The port 1 output buffers can sink/source four TTL inputs. When 1s are written to portn1 pins are pulled high by the internal pull-ups and can be used as inputs.
PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2 external counter inputs, read and write pins for memory access.
PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P2 will act as an address bus in conjunction with PORT P0 to access external memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1
PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P0 acts as a multiplexed address and data bus that can be used to access external memory in conjunction with PORT P2. P0 acts as AD0-AD7, as can be seen from fig 1.1
PORT P10: asynchronous communication input or Serial synchronous communication output.
[attachment=67438]
Introduction
LCD-based moving-message displays are becoming popular for transmitting information to large groups of people quickly. These can be used indoors or outdoors. We can find such displays in areas like railway platforms, banks, public offices, hotels, training institutes, nightclubs and shops.
The objective of the projects is to provide non-commercial and purely academic insight into microcontroller assembly programming. The over all goal of the projects is to provide connectivity between microcontroller and a HD44780 compatible LCD.
The LCD comes with a 14pin interface, which includes pins to receive power supply and ground as well. These 14pins have to be interfaced with microcontroller output ports to send instructions, which initialize the LCD in appropriate modes, and also to send data from the microcontroller is intended for display on the LCD output screen.
A string or message can be displayed on LCD by sending its characters to data register after configuring the command register of LCD. To create dynamic effects, a specific command instruction is sent to LCD via microcontroller AT89C51.
Moving message on LCD are ideal for all type of commercial establishments like Hotels, Restaurants, Retail Shops Banks, Airports, Clinics, Hospitals and other such places to get maximum attention of people. These displays attract customers to watch the display with curiosity and your scrolling message also is conveyed simultaneously.
BASIC PINS
PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller’s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)
PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only connect a crystal at these pins to provide clock pulses to the circuit.
PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V 500mA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.
PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If external memory is connected then PIN 31, also called EA/VPP, should be connected to ground to indicate the presence of external memory. PIN 30 is called ALE (address latch enable), which is used when multiple memory chips are connected to the controller and only one of them needs to be selected.We will deal with this in depth in the later chapters. PIN 29 is called PSEN. This is "program store enable". In order to use the external memory it is required to provide the low voltage (0) on both PSEN and EA pins.
PORTS
There are 4 8-bit ports: P0, P1, P2 and P3.
PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or additional functions associated with them based upon the context of their usage.The port 1 output buffers can sink/source four TTL inputs. When 1s are written to portn1 pins are pulled high by the internal pull-ups and can be used as inputs.
PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2 external counter inputs, read and write pins for memory access.
PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P2 will act as an address bus in conjunction with PORT P0 to access external memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1
PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P0 acts as a multiplexed address and data bus that can be used to access external memory in conjunction with PORT P2. P0 acts as AD0-AD7, as can be seen from fig 1.1
PORT P10: asynchronous communication input or Serial synchronous communication output.