MICROPROCESSOR A Microprocessor-based system From the above description, we can draw the following block diagram to represent a microprocessor-based system: Inside The Microprocessor • Internally, the microprocessor is made up of 3 main units. – The Arithmetic/Logic Unit (ALU) – The Control Unit. – An array of registers for holding data while it is being manipulated. Organization of a microprocessor- based system I/O Input / Output Memory ROM RAM System Bus ALU Register Array Control • Let’s expand the picture a bit. Memory • Memory stores information such as instructions and data in binary format (0 and 1). It provides this information to the microprocessor whenever it is needed. • Usually, there is a memory “sub-system” in a microprocessor-based system. This sub-system includes: – The registers inside the microprocessor – Read Only Memory (ROM) • used to store information that does not change. – Random Access Memory (RAM) (also known as Read/Write Memory). • used to store information supplied by the user. Such as programs and data. Memory Map and Addresses • The memory map is a picture representation of the address range and shows where the different memory chips are located within the address range. 0000 FFFF Address Range RAM 1 RAM 2 RAM 3 RAM 4 EPROM 0000 3FFF 4400 5FFF 6000 8FFF 9000 A3FF A400 F7FF Address Range of EPROM Chip Address Range of 1st RAM Chip Address Range of 2nd RAM Chip Address Range of 3rd RAM Chip Address Range of 4th RAM Chip Memory • To execute a program: – the user enters its instructions in binary format into the memory. – The microprocessor then reads these instructions and whatever data is needed from memory, executes the instructions and places the results either in memory or produces it on an output device. The three cycle instruction execution model • To execute a program, the microprocessor “reads” each instruction from memory, “interprets” it, then “executes” it. • To use the right names for the cycles: – The microprocessor fetcheseach instruction, – decodesit, – Then executesit. • This sequence is continued until all instructions are performed
Posted on: Wed, 26 Mar 2014 10:18:34 +0000
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