MICROPROCESSOR FUNCTION Technician Series Created Mar 2015 gmail.com

Microprocessor Function The microprocessor is a logic machine designed to follow a repeating cycle of reading an instruction and executing that instruction. The microprocessor relies on a built-in Instruction Set that internally steers the data and controls mechanisms toward its pre-programmed objective. The external instructions and data are obtained from sources such as memory (ROM or RAM), or Input systems (I/O) such as a keyboard or other external source. 2

Codes and Language The processor manipulates data in several different ways: Moves the data or addresses between different locations Add or subtracts values, more advanced devices can multiply, divide and square root Performs logic operations such as complementing, inverting, comparing, shifting, AND, OR, etc Instructions are in a binary pattern that the processor can interpret. This is called Machine Language. When writing programs people use mnemonics, a short abbreviated name, to make it easier to understand. This is called Assembly Language. 3

Codes and Language Assembly and Machine language are the lowest, most basic way of programming a device. It would be very time consuming and technically difficult to write an advanced set of codes or routines, called a program, using these basic languages. Higher level languages, called programming languages, are used to write more complex routines. Examples of high level languages include C, C++, Java, VHDL, etc…. A compiler is used to convert a high level language to a machine language that can be stored and used by the device. 4

Optcodes and Operands At the device level, the microprocessor processes instructions (OPTCODES) and data (OPERANDS). Sample of the Intel 8085 instructions (of 246 total), written in mnemonics: OPCODEOPERANDDescription MOVRd, RsCopy source register (Rs) to destination register (Rd) ADDMAdd content of memory to value in accumulator STA(address)Copy address in accumulator register to memory 5

Microprocessor Control 6

Control The microprocessor has numerous inputs and outputs for specific applications: Data/Instruction bus which is bi-directional (in or out of the processor) Address bus which is unidirectional (out of the processor) Control lines which can be inputs or outputs but are typically dedicated to specific purposes 7

Microprocessor System μPμP ROM RAM Output Register Input Register Other I/O Address Bus Data Bus Control 8

Selecting There are 2 primary ways a microprocessor enables a specific device on the data bus: Peripheral Mapping where the I/O or memory is selected directly through the use of control outputs. Memory Mapping where the I/O or memory is selected through the use of an address range. 9

Decoding an Address in Memory- Mapped I/O 10 Address 16-bit Upper 3 bits A 15 A 13 3 to 8 Decoder A B C Y0Y0 Y1Y1 Y2Y2 Y3Y3 Y4Y4 Y5Y5 Y6Y6 Y7Y7 Individual Device Enables

Device Select & Status S0, S1: Output indicates what step the micro is on in its processing cycle IO/M, Rd, Wr: Output to enable selected device ALE: Output states when address is on the AD bus 11

Basic Control X1, X2: Clock input CLK: Clock out to other devices Reset in, out: Reset applied to micro, it resets other devices Hold in: Stops microprocessor Hold Out: Micro acknowledges it is in a hold (stopped) state SOD, SID: Serial data in/out 12

Device Interrupt RST & INTR: input to the micro, to tell it to execute an instruction at a specific address 13

Support Circuitry The instructor will provide a handout to analyze 14

Programmable Logic 15

Electronic Trends When learning electronics we used discrete single- function chips as part of the lab activities. Electronics today is very different. What is more commonly used are programmable logic devices: CPLD (Complex Programmable Logic Devices) for basic digital logic operations FPGA (Field Programmable Gate Arrays) for more advanced digital logic functions ARM and microcontrollers such as Arduino, Stamp, and many others for processing capabilities and may be fully functional computers with integrated RAM, ROM, I/O 16

Embedded Systems An embedded system is a computer that is designed and used as a dedicated function. Advantages of embedded systems are numerous: Size, power consumption and price is reduced. May be highly portable. Integrated functions further reduce the amount of support circuitry needed. Examples include ADCs, integrated sensors. Very efficient at its specific task. Firmware may be updated. Programmable logic is more universal, smaller, easily modified, designs are easily transported, etc. 17

Examples of Embedded Systems You likely own many embedded systems: Computer (devices such as HDD, MB and other peripherals have embedded systems) Printer Cell Phone (typically ARM-based) MP3 Player Remotes Calculators Digital Camera Newer vehicle Newer appliances such as dishwashers, clothes washers, microwaves, televisions and even toasters may have embedded systems. 18

Embedded Systems Embedded Systems have several significant disadvantages to a technician: The physical chip may be custom-made or otherwise unavailable The chips are not universal and must remain with the specific vendor The chip may be impossible to physically access The software to program the device is device-specific and may be very expensive The program written for the embedded chip is proprietary and will not be generally available The device input/output values and configurations may be unknown, so it may be difficult to determine if the device is functioning properly. 19

Embedded System The instructor will hand out diagrams to analyze END 20