Applications of Microprocessor 8086 on Outer Peripherals

Topics: Cathode ray tube, X86, Liquid crystal display Pages: 6 (1660 words) Published: February 10, 2011
Vishal Dahuja B.Tech. - CSE RC1701A’29’ Reg. No # 1050070024

1. INTRODUCTION The 8086 microprocessor is the 16 bit microprocessor which means that the arithmetic logic unit, its internal registers and also the data bus these entire have to work with 16 bit at a time. The microprocessor has 20 bit address bus and therefore 220 memory locations. The pin diagram of 8086 is as shown: The 8086 microprocessor is just like 8085 microprocessor but the difference between them is that the 8085 microprocessor is of 8 bits but that of the 8086 is the 16 bit microprocessor. Also the flags are more in case of the 8086 microprocessor as shown:

Figure 1.2

The flags are as described below:
Figure 1.1

Overflow Flag (OF) - Set if the result is too large positive number, or is too

small negative number to fit into destination operand.  Direction Flag (DF) - if set then string manipulation instructions will auto-decrement index registers. If cleared then the index registers will be auto-incremented. Interrupt-enable Flag (IF) - setting this bit enables mask-able interrupts. Single-step Flag (TF) - if set then single-step interrupt will occur after the next instruction. Sign Flag (SF) - set if the most significant bit of the result is set. Zero Flag (ZF) - set if the result is zero. Auxiliary carry Flag (AF) - set if there was a carry from or borrow to bits 0-3 in the AL register. Parity Flag (PF) - set if parity (the number of "1" bits) in the low-order byte of the result is even. Carry Flag (CF) - set if there was a carry from or borrow to the most significant bit during last result calculation.

    

Figure 2.1

Actually we know in order to give directions or data values to the users, many of the microprocessor-controlled instruments and machines need to display the letters of the alphabets and the numbers, if some large amount of the data is needed to be displayed there the CRT is used and for the small amount of data the digital displays are used. Some of the technologies are the LED displays and the LCD displays. 2.1 LCD

2. OUTER PERIPHERALS Outer peripherals refer to the peripherals that are used for getting the output. The most simple and the famous and the foremost term that come to our mind is the display devices. The different types of the displays are:

Liquid Crystal Displays are created by placing a thin (approximately 10 mm) layer of liquid crystal fluid between two glass plates. A transparent electrically conductive film is placed on the rear glass plate. Transparent sections of the conductive film in the shape of characters are coated on the front glass. Voltage is applied between the LCD segment and the backplane. This produces an electric field region under the segment. The electric field changes the transmission of the light through the region under the segment film. In this we have the following components: 1) Decoder 2) HD44780 controller

This procedure of the making of LCD can be shown by:

The circuit diagram can be as such:

Figure 2.1.1

In the interfacing of the 8086 with that of the LCD we need 8255 that is just used for the interfacing between them. The pin diagram of the 8255 is as such: Description: The LCD module has in built controller driver HD44780 as mentioned above with a 14 dual row header. This can be interfaced with a 4-bit and 8-bit data bus. This pin out includes 8 data lines (DB7DB0), three control signal (RS- Register Select, Read write and enable) and three connection for the power and the ground supply. The controller has two 8-bit control registers (instruction register (IR) and data register (DR)). Whenever the MPU writes into one of the register the controller sets the data line DB7 high as a busy flag and on the completion of the operation it resets the busy flag. The LCD is interfaced by using 8255 that is selected by the signal generated by address...
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