01 introduction to microcomputers
- 1. 1/15/2010 1 Lecture 1: Introduction to Microcomputers Today’s Topics • What is a microcomputers? Wh do e st d microcomp ters?• Why do we study microcomputers? • Two basic types of microcomputer architectures • Internal components of a microcomputers
- 2. 1/15/2010 2 Microcomputer • Major components of the computer - the processor, the control unit, one or more memory ICs, one or more I/O ICs, and the clock • A single printed circuit board usually connects the ICs, making a computer called a microcomputer Memory Data/Instructions Address/Control Microprocessor Processor (ALU) Control Unit Input / Output Clock Status/Control Data Input Output Microprocessor Another definitions • Microcomputer – Relatively small and inexpensive computer that is contained on Microcomputers, Microcontrollers, and Microprocessors one or a few chips • Microcontroller – A single-chip microcomputer • Microprocessor – The processor and control unit part of the single-chip computer(=microcontroller) is called microprocessor. There is no single and clear definition of these terms.
- 3. 1/15/2010 3 Why do we study Microcomputers? • Embedded systems use microcontrollers or microcomputers. Some interesting statistics (from a fe ears ago)• Some interesting statistics (from a few years ago) – An average American interacts with 300 or more embedded systems every day. – 95% of all microprocessor will be sold each year for embedded systems. – IEEE estimated that over 700,000 people worldwide were employed writing code for embedded system in 2007. Basic Architecture • There are many other architectures in use. They will be discussed in a computer architecture course. Princeton and Harvard What are ….? • Here, we will cover two major architecture of microcomputers. – Princeton and Harvard architecture – The main difference is the memory structure • Princeton Architecture* – Known as Von Neumann architecture – Single memory contains both the program code and the dataSingle memory contains both the program code and the data. • Harvard Architecture – Two separate memories. One contains only data while the other is containing only program code.
- 4. 1/15/2010 4 Princeton Architecture • No separate memory space for program code and data Known as Von Neumann Memory Data/Instructions Address/Control D t Input Microprocessor Processor (ALU) Control Unit Input / Output Clock Status/Control Data Output Harvard Architecture • Two separate memory units • The length of an instruction could be different from the data size OK.. I see. One clear distinction of these two is whether two separate memory units exist or not. • Both data and a program instruction can be read at the same time Data Memory Instructions D t Input Microprocessor Code Memory Data Address /Control Processor (ALU) Control Unit Input / Output Clock Status/Control Data Output
- 5. 1/15/2010 5 Major components • Also called an arithmetic logic unit (ALU). Operations s ch as addition s btraction bit ise AND and 1. Processor • Operations such as addition, subtraction, bit-wise AND and OR, shift operations. • The processor has registers (groups of D flip-flops used to store binary values). • Many microcontrollers perform operations on data that is located in a register. This requires the microcontroller to load h d f hthe data from memory into a register in the processor, manipulate the data, then store the new value back to memory. • The processor also generates signals that indicates when values are negative, zero, or when arithmetic overflow occurs. Major components • A synchronous sequential machine that coordinates the flow of data between the other units and operations of the other bl k 2. Control Unit blocks. • The sequence of states and control output of the unit depend on the inputs: the current program instruction, the status outputs of the other blocks, and the input/output block. • Generally speaking, central processing unit (CPU) refers to not only the processor but also the control unit.
- 6. 1/15/2010 6 A Quick Introduction of HCS12 Microcontroller • The Motorola 68HC12 was introduced in 1996 as an upgrade for the 68HC11. HCS12 (=68HC12 or 9S12) family microprocessor • Features – 16-bit CPU – Standard 64-KB address space support – Multiplexed (address and data) external bus. – 0 to 4 KB of on-chip EEPROM – 2 KB to 14 KB of on-chip SRAM 10 bit A/D t– 10-bit A/D converter – 16 KB to 512 KB of on-chip flash memory (or ROM) – Etc. etc. etc. Major components • Memory is the place where program code and data are stored. A seq ence of directl addressable ‘locations ’ 3. Memory • A sequence of directly addressable ‘locations.’ • Therefore, the number of addresses available in a memory is limited by the number of bits used to represent the address. • If 16 bits are used for the address, there are 65,536 (=216) different addresses available.
- 7. 1/15/2010 7 Major components • A memory location is referred to as an information unit which has two components: its address and its contents. 3. Memory - continued • The content indicated by an address can be interpreted by the microprocessor as one of t o things CPU Memory Address bus lines Data bus lines microprocessor as one of two things. – Instruction code are used as inputs into the control unit and determine how it operates. A group of instruction is called a program. – Data are the numbers to be processed or the results of operations in the processor. Major components • A periodic signal for the sequential machine in the control unit. 4. Clock • Also used by other blocks to synchronize operations
- 8. 1/15/2010 8 Major components • The Input/Output (I/O for short.) block represents the interface between the internals of the microcomputer and the d ld 5. Input/Output outside world. • Keyboard, LED and LCD display, printers for example. Instruction Codes • Instruction codes consist of Operation Code and Operand Operation Code (Op Code for short)• Operation Code (Op Code for short) – This tells the microcomputer what action to perform and how to interpret the operand. All instructions must have an op code. • Operand – The operand contains the data that microcontroller will perform the action on. – Some operands include several numbers for op codes that specify more complex actions. – Some operation codes that perform simple tasks do not need to have operands.
- 9. 1/15/2010 9 Instruction Length • Fixed length – Each instruction is the same number of bits as all others. Fixed and Variable-length • Variable length* – The length of each instruction may be different. Op Code 1 Operand Op Code 2 Operand Op Code 3 Operand Op Code 1 Operand Op Code 3 Operand Op Code 2 Operand Questions?
- 10. 1/15/2010 10 Wrap-up • The definitions of microcomputers, microcontroller, and microprocessor What we’ve learned • The importance of microcomputers in the real world • Princeton* and Harvard architectures • Processor, control unit, memory, clock, and I/O are the major components of microcomputers. Now.. I get the clear picture what the microcomputers are. And I feel like that this is going to be really fun. What to Come • Review number systems Introd ction to the HCS12/9S12• Introduction to the HCS12/9S12