lecture2 - EEL 4744C: Microprocessor Applications Lecture 2...

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Dr. Tao Li 1 EEL 4744C: Microprocessor Applications Lecture 2 Programming Model, Address Mode, HC12 Hardware Introduction
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Dr. Tao Li 2 Microcontrollers and Microcomputers: Chapter 3, Chapter 4 Software and Hardware Engineering: Chapter 2 Or Software and Hardware Engineering: Chapter 4 Plus CPU12 Reference Manual: Chapter 3 M68HC12B Family Data Sheet: Chapter 1, 2, 3, 4 Reading Assignment
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Dr. Tao Li 3 EEL 4744C: Microprocessor Applications Lecture 2 Part 1 CPU Registers and Control Codes
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Dr. Tao Li 4 Accumulators Registers that accumulate answers, e.g. the A Register Can work simultaneously as the source register for one operand and the destination register for ALU operations General-purpose registers Registers that hold data, work as source and destination register for data transfers and source for ALU operations Doubled registers An N-bit CPU in general uses N-bit data registers Sometimes 2 of the N-bit registers are used together to double the number of bits, thus “doubled” registers CPU Registers
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Dr. Tao Li 5 Pointer registers Registers that address memory by pointing to specific memory locations that hold the needed data Contain memory addresses (without offset) Stack pointer registers Pointer registers dedicated to variable data and return address storage in subroutine calls Index registers Also used to address memory An effective memory address is found by adding an offset to the content of the involved index register CPU Registers (2)
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Dr. Tao Li 6 Segment registers In some architectures, memory addressing requires that the physical address be specified in 2 parts Segment part : specifies a memory page Offset part : specifies a particular place in the page Condition code registers Also called flag or status registers Hold condition code bits generated when instructions are executed, e.g. overflow in ADD CPU Registers (3)
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Dr. Tao Li 7 MOV A, B B is the source, A is the destination ADD A, B Add (A) to (B), then transfer the answer from ALU to A Register transfer language Register name in () means “content” of the register ” means replacement, e.g. (A) (B) Register Transfers
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Dr. Tao Li 8 Also called flag or status registers Contain bits that are set or reset due to instructions ALU, load or move can all modify the CCR Most processors also provide instructions that modify the CCR directly What are the “bit” in the CCR? Condition Code Register (CCR)
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Dr. Tao Li 9 Carry bit Set to 1 if there is a carry/borrow out of the most significant bit during an ADD or SUB Overflow The result is too large to be represented by available bits Underflow The result is too small to be represented by available bits Examples: 10010011 (147 10 ) +/- 10110011 (179 10 ) ADD gives overflow , SUB gives underflow , setting the carry (or borrow) bit to 1 Condition Code Register (2)
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Dr. Tao Li
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This note was uploaded on 11/13/2011 for the course EEL 4744c taught by Professor Staff during the Fall '09 term at University of Florida.

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lecture2 - EEL 4744C: Microprocessor Applications Lecture 2...

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