Introduction to Hardware ET-8031/51 KIT:

1. General: 8-bit 8031/8051 microcontroller operating at 10/12 MHz with on-chip oscillator and clock circuit, 8 i/o lines, two 16-bit timers/counters, five sources of interrupt structure. 64 KB of external program memory and 64 KB of data memory.
2. Memory: Kit has 8KB RAM using IC 6264 and 32KB of EEPROM monitor using IC 27256 There is a memory space provided for memory expansion, the space can be defined for an address from 4000 – FFFF depending upon size of memory chip to be used.
3. I/O Devices: The kit uses 8279 programmable KB-display controller, 8253- programmable interval timer, 8255 –programmable peripheral interface, peripheral chips. These are explained below:
   1. 8279 –Programmable KB and display controller:It is a general purpose  Programmable KB and display interface device designed for use with 8031/8051 microcontroller and for the microprocessors. It provides a scanned interface to 28 contact key matrix provided in the KIT and scanned interface for the six seven segment display. 8279 has got 16*8 display RAM which can be loaded or interrgogated by the CPU. When a key is pressed, its corresponding code is entered in the FIFO queue of 8279 and can now be read by the microcontroller. 8279 also refreshes the display RAM automatically.
   2. 8255- Programmable peripheral interface IC: This IC basically acts as a general purpose i/o device to interface peripherals equipment to the system BUS. It is not necessary to have the external logic to interface with the peripheral device since the function configuratyion of 8255 is programmed by the system software. It has three 8-bit ports (A,B,C) Port C can be divided into two 4-bit ports C_upper and C. Any combination of Port A,B and C can be defined using appropriate software commands
   3. 8253: Programmable interval Timer: It can be used forgeneration of accurate time delays under the software control. Various other functions that can be implemented with this chip are programmable rate generator, event counter, binary rate multiplier, real time clock etc. It has three independent 16-bit counters, each having a count rate of 2KHz. First counter is used for single step operation. However its connection is also broughtat connector space J2. For single step operation CLK0 signal of counter 0 is getting the clock frequency of 1.535 MHz. Counter 1 and 2 are free for user. Clock for CLK1 and CLK2 is to be given externally.
   4. 8251 USART: This is a programmable communication interface and is used as a –peripheral device. This device accepts data characters from CPU in parallel format and then convertes into serial data characters for the CPU. This chip will signal whenever it accepts a new character for the CPU. The CPU can read the complete status of it at any time. 8251 has been initialized in the kit for AUX RS-232C interface.
4. Process Control Chips: The kit has ADC 0809 A/D Convereter, DAC 0800, Relay, and MC2TE opto isolator and display
   1. ADC 0809 A/D converter: It is a successive approximation type of A/D converter and is a monolithic CMOS converter having conversion time of 100 micro sec. It has 8-channel of A to D having 8-bit accuracy. It selects one of the 8-channels by using the address decoder. Input is latched to the decoder on the low to high transition of the address latch enable (ALE) signal. The conversion starts on the falling edge of the start conversion signal. During the process END of conversion signal goes low otherwise it remains high. Digital output can be read from the ADC making the output enable signal high.
   2. 0800 DAC: It is a monolithic 8-bit high speed current output DAChaving settling time of 100 nano sec. It has full scale error of the +/- 1 LSB and can operate under wide power supply range of +/- 5.4V to +/- 18V
   3. DIP switches: DIP switch provides two double throw contacts. The relay operates at +5V supply and is available in DIP package.
   4. MCT2E (Opto Isolator) : Optocoupler consisiting of Gallium Aresnide infrared emitting diode as the input stage and a silicon npn photo transistor as the output stage. The coupling medium between diode and sensor is an infrared transmitting glass. A current source between  the collector and base of the sensor is used to represent the virtual base current generator by incident photons striking the base. The base current is proportional to the amount of radiation emitted from the diode. A relatively large transistor base area is necessary for increasing the sensor efficiency.
   5. Display: It has a six digit seven segment display. First four digits are for address and last two digit for Hex value.

ET-8031/51