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Microprocessors-based systems (under graduate course) Lecture 1 of 9
The document is a lecture on microprocessor-based systems by Dr. Randa Elanwar, covering essential topics such as microprocessor definitions, architecture including the 8086 microprocessor, and components like the CPU, memory, and input/output circuitry. It explains binary information representation, bus structures, instruction execution processes, and compares various microprocessors including the 8086 and 8088. Additionally, the document discusses bus architecture, instruction sets, and examples related to microprocessor operations and data processing.
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Microprocessors-based systems (under graduate course) Lecture 1 of 9
- 1. Microprocessor-Based Systems Dr. RandaElanwar Lecture 1
- 2. Lecture Content • Introductionto microprocessors, • Comparison of typical microprocessors • The 8086 microprocessor architecture: – The microprocessor system: CPU, memory, I/O – The microprocessor Pin outs, clock circuitry, – Bus structure: address bus, data bus, and control bus connections – The microprocessor instruction sets 2Microprocessor-Based Systems Dr. Randa Elanwar
- 3. Introduction to microprocessors •Definition: Microprocessor • Is a digital integrated circuit(s) capable of executing program • Definition: Program • Is a set of instructions to be executed in sequence • Definition: Central processing unit (CPU) • Is a logic circuit controlling the operation of the computer • Microprocessors perform the function of a CPU in micro- computer systems. 3Microprocessor-Based Systems Dr. Randa Elanwar
- 4. Introduction to microprocessors •Microprocessors started at mid 70’s • The data/information processed by a microprocessor (electronic circuits) is usually represented in binary format. • Each binary digit represent a power of 2. A binary digit is often called a ‘bit’ • The binary system uses only two symbols zero (0) and one (1) • Binary numbers are often called ‘binary words’. • A 4-bit binary word is called a ‘nibble’. • An 8-bit binary word is called a ‘byte’. • A 16-bit binary word is called a ‘word’. • A 32-bit binary word is called a ‘long word’/‘double word’. 4Microprocessor-Based Systems Dr. Randa Elanwar
- 5. Introduction to microprocessors •Binary information is fed to the electronic circuits by voltage levels. • Standard logic circuits use 5 volts power supply. • Low voltage circuits use 3 volts power supply, thus consumes less power as in portable computers. 5Microprocessor-Based Systems Dr. Randa Elanwar •Binary information is =1 if 3v <= voltage <= 5v, and information is =0 if 0v <= voltage <= 1v •If 1v < voltage < 3v, the binary information level is considered undefined. Low High Undefined 0 v 1 v 3 v 5 v
- 6. Introduction to microprocessors •The simple microprocessor major parts are: The central processing unit (CPU), memory, and the input/output circuitry. • Connecting these three parts are three sets of parallel lines called buses. The three buses are the address bus, the data bus and the control bus. 6Microprocessor-Based Systems Dr. Randa Elanwar
- 7. Introduction to microprocessors TheCentral Processing Unit (CPU) • The CPU controls the operation of the computer. • The CPU fetches binary coded instructions from memory, decodes the instructions into simple actions and carries out these actions in sequence of steps. • The CPU also contains an “address counter”, which holds the address of the next instruction or data item to be fetched from memory or temporary storage registers. 7Microprocessor-Based Systems Dr. Randa Elanwar
- 8. Introduction to microprocessors Memory •Memory has 2 purposes: store the binary codes of instructions to be carried out and store the binary coded data with which the computer is going to be working. • Memory types are either ROMs or RAMs. These are implemented using logical gates circuitry (e.g. D flip flops) 8Microprocessor-Based Systems Dr. Randa Elanwar Clock + - Clock (CLK)
- 9. Introduction to microprocessors •If the flip flop is +ve edge sensitive, the output (Q) will be equal to the input (D) only at the +ve edge of the clock (active high) • If the flip flop is -ve edge sensitive, the output (Q) will be equal to the input (D) only at the -ve edge of the clock (active low) 9Microprocessor-Based Systems Dr. Randa Elanwar
- 10. Introduction to microprocessors •Example (active high) 10Microprocessor-Based Systems Dr. Randa Elanwar Input Output CLK
- 11. Introduction to microprocessors •Inputs and Outputs (I/O) • The I/O section allows the computer to take in data or send out data. • Peripherals such as keyboards, monitors, printers and modems are connected to the I/O section through ports. • The simplest type of input or output port is just a set of parallel D flip-flops (Register) Example: 8 bit register 11Microprocessor-Based Systems Dr. Randa Elanwar
- 12. Introduction to microprocessors •Inputs and Outputs (I/O) • In the 8 bit register we have 1 pin for GND, 8 pins for inputs, 8 pins for outputs, 1 for clock and 2 for supply (20 pins) • For an input port, the D inputs will be connected to the external device and the Q outputs will be connected to the data bus which runs to the CPU. • For an output port, the D inputs will be connected to the data bus which runs to the CPU and the Q outputs will be connected to the external device. • In either cases the data is transferred to/from the bus is enabled only when receiving a control signal from the CPU (usually the clock) 12Microprocessor-Based Systems Dr. Randa Elanwar
- 13. Introduction to microprocessors •Example: • It is not a must that the data stored in register A is the same stored in register B because this depends on their clocks. • In most cases a master clock only is available thus we need another control signal such that data goes to/from the intended registers only (chip selection CS) 13Microprocessor-Based Systems Dr. Randa Elanwar Reg A Reg B 8 input lines CLKA CLKB
- 14. Introduction to microprocessors •Example: to transfer data from Reg A to Reg B 14Microprocessor-Based Systems Dr. Randa Elanwar Reg A Reg B 8 input lines CLKA CLKB CSA CSB CSA CLKB
- 15. Introduction to microprocessors •The address bus • It consists of 16, 20, 24, 32 parallel signal lines. On these lines the CPU sends out the address of the memory location that is to be written to or read from. • The number of memory locations that the CPU can address is determined by the bus size. • If the CPU has N address lines it can address 2N memory locations. 15Microprocessor-Based Systems Dr. Randa Elanwar # Address lines # Memory locations 16 65,536 20 1,048,576 24 16,777,216
- 16. Introduction to microprocessors •The data bus • It consists of 8, 16 or 32 parallel signal lines. They are bidirectional lines. • The CPU can read data from memory/port and write data to memory/port on these lines. • Many devices have their outputs connected to the data bus thus they must have a selection signal. • The control bus • It consists of 4 to 10 parallel signal lines. • The CPU sends out signals on the control bus to enable the outputs of addressed memory or port devices. • Typical control bus signals are Memory Read, Memory Write, I/O Read and I/O Write. 16Microprocessor-Based Systems Dr. Randa Elanwar
- 17. Introduction to microprocessors •Example: Memory Read • To read a byte of data from a memory location, the CPU sends out the memory address of the desired byte on the address bus and then sends out a Memory Read signal on the control bus. • The Memory Read signal enables the addressed memory device to output a data word onto the data bus. • The data word from memory travels along the data bus to the CPU. • Example: 3 Instructions program 1. Input a value from a keyboard connected to the port at address 05H 2. Add 7 to the value read in 3. Output the result to a display connected to the port at address 02H 17Microprocessor-Based Systems Dr. Randa Elanwar
- 18. Introduction to microprocessors 18Microprocessor-BasedSystems Dr. Randa Elanwar
- 19. Comparison of typicalmicroprocessors 19Microprocessor-Based Systems Dr. Randa Elanwar 8086 8088 16 bit microprocessor, 16 bit data bus, 20 bit address bus 16 bit microprocessor, 8 bit data bus, 20 bit address bus The arithmetic logic unit has internal registers Same as 8086 Instructions work with 16 bit binary words Same as 8086 Read/write data either 8 or 16 bit at a time Read/write data either 8 bits at a time Can address 220 memory locations Can address 220 memory locations Reads 16 bit word in 1 operation Reads 16 bit word in 2 operations The 80186 is an improved version of 8086 and 80188 is an improved version of 8088 with instruction set that is a superset of the instruction set of the 8086. Both are 16 bit microprocessors. The 80286 is a 16 bit microprocessor advanced version of the 8086 designed for multitasking microcomputers. The 80386 is a 32 bit microprocessor which can address up to 4 gigabytes memory used in multitasking microcomputers. Self study: you can read more about the competitive microprocessors and find out the aspects of comparison
- 20. Microprocessor bus architectureand instruction sets • Before we talk about how to write a program for the 8086 we first have to discuss its internal features: ALU, flags, registers, instruction byte queue and segment registers. • The 8086 CPU is divided into 2 independent functional parts: 1. Bus interface unit (BIU): sends out addresses, fetches instructions from memory, reads/writes data from/to ports and memory 2. Execution unit (EU): tells the BIU where to fetch the instructions and data from, decodes and execute instructions 20Microprocessor-Based Systems Dr. Randa Elanwar
- 21. Microprocessor bus architectureand instruction sets 21Microprocessor-Based Systems Dr. Randa Elanwar To understand this architecture and function of each component we will have to discuss several simpler structures
- 22. Microprocessor bus architectureand instruction sets • Example 1: Simple bus architecture 22Microprocessor-Based Systems Dr. Randa Elanwar Reg A Reg BCLKA CLKB CSA CSB Reg C Reg D CLKC CLKD CSC CSD CLRD Reg E CLKE CSE CNT Up CNT DN •In this architecture we have 3 registers with CS signal (A, B and C) •Reg D has an active low CLR signal •Reg E has two active low signal (CNT UP) to increment its contents by 1 at every –ve edge and (CNT DN) to decrement its contents by 1 at every –ve edge •We will discuss how this architecture executes these simple instructions: MOV B, A CLR A INC B
- 23. Microprocessor bus architectureand instruction sets 23Microprocessor-Based Systems Dr. Randa Elanwar CSA CLKB MOV B, A: means move the content of A to B We select Reg A to output data on bus We activate Reg B clock to read the data on bus CLR A: Reg A doesn’t have a CLR signal input Use Reg D to clear its content move this content to Reg A (MOV A, D) CSD CLKA CLRD PD PD CSB CLKE CSE CLKB CNT UP INC B: Reg B doesn’t have a CNT UP signal input move this content to Reg E (MOV A, E) Use Reg E to increment its content move this content to Reg B (MOV B, E) PD: propagation delay
- 24. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 24Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode In this architecture: Reg A is known as “Accumulator” i.e. accumulate results of ALSU
- 25. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 25Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode The buffer is used to isolate the output of Reg A if CSA is low and as a 8 bit buffer if CSA is high
- 26. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 26Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode T1 is a temporary register. Takes the input only from the bus and outputs its content as ALSU Yin. Doesn’t have to be isolated, has no CS control line
- 27. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 27Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode ALSU: Arithmetic Logic Shift Unit. It does binary/decimal arithmetic operations (+,- ,*,/), logic operations (>,=,<,complement) and shift operations
- 28. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 28Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode If we want to add A and B: ADD A, B Means A+BA The micro-operations will be: 1. Move B to T1 2. Select ALSU addition Mode 3. Set CSALSU low (result Z is on the bus) 4. Set CLKA low to move (A takes the result)
- 29. Microprocessor bus architectureand instruction sets • Example 2: Advanced bus architecture 29Microprocessor-Based Systems Dr. Randa Elanwar Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD Reg E CLKE CSE CLKT T1 CF CSALU Xin Yin Z ALSU mode CF: Carry flag, a flip flop that holds the carry for arithmetic operations To avoid racing (continuous addition, we introduce time delay between input A (Xin) and output A (Z) using a master-slave flip flop To add Reg B and C for example we need a new architecture
- 30. Microprocessor bus architectureand instruction sets • Example 3: Advanced bus architecture 30Microprocessor-Based Systems Dr. Randa Elanwar T2 CLKT2 Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD CLKT1 T1 CF CSALU Xin Yin Z ALSU mode Now if we want to add B and C and store the result in D The micro-operations will be: 1. Move B to T1 2. Move C to T2 3. Select ALSU addition Mode 4. Set CSALSU low (result Z is on the bus) 5. Set CLKD low to move (D takes the result)
- 31. Microprocessor bus architectureand instruction sets • Example 3: Advanced bus architecture 31Microprocessor-Based Systems Dr. Randa Elanwar T2 CLKT2 Reg A CLKA CSA Reg B CLKB CSB Reg C CLKC CSC Reg D CLKD CSD CLKT1 T1 CF CSALU Xin Yin Z ALSU mode Thus structure enables the addition of 1 byte to 1 byte Ex: 0011 1010 + 1011 1100 1111 0110 cc c Multi-byte addition needs store the carry in a D flip flop Carry flag