1. Computer Architecture and MicroprocessorsBy
Navdeep Goyal

2. Purpose of Talk
What are the advantages of teaching these topics to physics students
To discuss the curriculum for teaching microprocessors to physics students
Introduction to SAP-1
8085 microprocessor

3. Importance
. Learning about the design considerations of microprocessors is important . Students opting for further studies in microelectronics are benefitted . Knowledge of working of a processors is important . Starting with working of simplest computer system is always helpful . Better to start with few basic principles of working of computer systems

4. Proposed Sequence Which device was designed first
Computer or microprocessor?
Bus organised computer systems
Data Bus
Address Bus
Control Bus
Tri-state Devices
Buffer Registers
SAP-1, SAP-2 etc
8085 microprocessor
8086 and other advanced microprocessors

5. BUS SYSTEM
In all computer system, the data is transferred from one place to other through common DATA BUS
The selection of device is from the address, which is sent through common address bus
Depending upon control signals data is written onto or read from a particular register

6. TRI STATE DEVICES
TRI-STATE Devices play important role when we are dealing with bus organized computer systems
Three terminal device:
Input, output, control
Available in high active or low active mode
Used at the output of registers, which are connected with common data bus

7. Buffer Registers
The loading of data and reading data from buffer register is with the help of control signals
For loading data onto register a Load (L) signal is used
For receiving data from buffer register an Enable (E) signal is used
For different registers loading or enabling may be high or low active

8. Introduction to Sap-1 SAP-1 stands for simple as possible computer
SAP-1 is a computer made from discrete IC’s
Its an 8 bit computer with 4 address lines
Can handle max. of 16 address locations
Instruction set includes instructions
LDA, ADD, SUB, OUT, HLT

9. OPCODES
LDA 0000
ADD 0001
SUB 0010
OUT 1100
HLT 1111

10. OPCODES AND OPERAND
Complete code includes opcode and operand Like LDA 04H One instruction is executed in one instruction cycle

11. Machine Cycle/Instruction Cycle
Instruction cycle may consist of many machine cycles
For SAP-1, Instruction cycle= machine cycle
Instruction cycle=Fetch cycle+Execution Cycle
Fetch cycle is generally same for all instructions

12. Ring Counter

13. SAP-1

14. How to fabricate various units
Program Counter: 4 bit counter-made from J-K flip-flops-74 LS107 with 74LS126
Input/MAR: includes address/data switch registers includes buffer register and 2-1 multiplexer
16X8 RAM
Instruction Register: 8 bit buffer register , 2 nos 74 LS173
Controller Sequencer: to generate control signals
Accumulator: Buffer register to store intermediate results
Adder Subtracter: Arithmatic unit
B: buffer register

15. Control Signals Fetch T1 0 1 0 1 1 1 1 0 0 0 1 1

16. Control Words for various instructions

17. Control Unit of SAP-1

18. Microprogrammed Control Unit
Easier to fabricate
Slower-not useful for commercial microprocessors
Can be used for testing various instructions

19. Variable Machine Cycle
Fixed machine cycle may give many unwanted time states
Execution is going to take longer time
Better to opt for variable machine cycle

20. 8085 Pin Diagram

21. Architecture of 8085

25. Thanks