Microprocessor

Practical-Introduction to Microprocessor

Aim

To study the microprocessor 8085

Architecture of 8085 Microprocessor

  a.     General purpose register
     The register B,C,D,E,H,L is known as general purpose register. Each register have 8-bit space to store 8-bit data (i.e. each register make by combination of  8-flip-flop circuit , one flip-flop store 1-bit data).
     The combination of 8 bit register is known as register pair, which can hold 16 bit data.

  b.    Accumulator
     Accumulator is a 8-bit register, which hold one of the data to be processed by ALU and stored the result of the operation.

  c.     Program counter (PC)
     Program counter is a 16-bit register, which have the address of next instruction.(i.e. in 8085 the execution of program is start from PC.)

  d.    Stack pointer
     Stack pointer is a 16 bit special purpose register which is used to hold line memory address for line next instruction to be executed.

  e.     Arithmetic and Logic unit
     Arithmetic and Logic unit carries out arithmetic and logical operation by 8 bit address it uses the accumulator content as input the ALU result is stored back into accumulator.

  f.      Temporary register
     It is an 8 bit register associated with ALU hold data, entering an operation, used by the microprocessor and not accessible to programs.

  g.     Flags
     Flag register is a group of fire, individual flip flops line content of line flag register will change after execution of arithmetic and logic operation. The line states flags are.
i) Carry flag (C)
ii) Parity flag (P)
iii) Zero flag (Z)
iv) Auxiliary carry flag (AC)
v) Sign flag (S)

  h.    Timing and control unit
     Synchronous all microprocessor, operation with the clock and generator and control signal from it necessary to communicate between controller and peripherals.

  i.       Instruction register and decoder
    Instruction is fetched from line memory and stored in line instruction register decoder the stored information.

j j.       Register array
   These are used to store 8 bit data during execution of some instruction. If we want to store 16-bit data then we use pair of register i.e. B-C, D-E, H-L.

Pin Description

Address Bus

1. The pins Ao – A15 denote the address bus.

2. They are used for most significant bit

Address / Data Bus

1. AD0 – AD7 constitutes the address / Data bus

2. These pins are used for least significant bit

ALE : (Address Latch Enable)

1. The signal goes high during the first clock cycle and enables the lower order address bits.

IO / M

1. This distinguishes whether the address is for memory or input.

2. When this pins go high, the address is for an I/O device.

S0 – S1

S0 and S1 are status signal which provides different status and functions.

RD

1. This is an active low signal

2. This signal is used to control READ operation of the microprocessor.

WR

1. WR is also an active low signal

2. Controls the write operation of the microprocessor.

HOLD

1. This indicates if any other device is requesting the use of address and data bus.

HLDA

1. HLDA is the acknowledgement signal for HOLD

2. It indicates whether the hold signal is received or not.

INTR

1. INTE is an interrupt request signal

2. IT can be enabled or disabled by using software

INTA

1. Whenever the microprocessor receives interrupt signal

2. It has to be acknowledged.

RST 5.5, 6.5, 7.5

1. These are nothing but the restart interrupts

2. They insert an internal restart junction automatically.

TRAP
1.  Trap is the only non-maskable interrupt
2.  It cannot be enabled (or) disabled using program

RESET IN
1.  This pin resets the program counter to 0 to 1 and results interrupt enable and HLDA flip flops.

X1, X2
1.  These are the terminals which are connected to external oscillator to produce the necessary and suitable clock operation.

SOD
1.  This pin provides serial input data

SOD

1.     This pin provides serial output data

VCC and VSS

1. VCC is +5V supply pin

2. VSS is ground pin

IC’s Used

8085 - 8 bit p

8253 - programmable internal timer

8255 - programmable peripheral interface

8279 - programmable key boards / display interface

8251 - programmable communication interface

2764 - 8 KV VV EPROM

6264 - 8K STATIC PROM

7414 - Hex inverter

7432 - Quad 21/p OR GATE

7409 - Quad 21/p AND GATE

7400 - NAND Gate

7404 - Dual D-FF

74373 - Octal ‘D’ Latch

74139 - Dual 2 to 4 line decoder

74138 - 3 to 8 line decoder

In Enter Program into Trainer Kit

1. Press ‘RESET’ key

2. Sub (key processor represent address field)

3. Enter the address (16 bit) and digit in hex

4. Press ‘NEXT’ key

5. Enter the data

6. Again press “NEXT”

7. Again after taking the program, are use HLT instruction its Hex code

8. Press “NEXT”

How to executive program

1. Press “RESET”

2. Press “GO”

3. Enter the address location in which line program was executed

4. Press “Execute” key

Results

Thus 8085 microprocessor was studied successfully.