Lecture03_handout-F09

Lecture03_handout-F09 - CE-320 Microcomputers I Fall B 2009...

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CE-320 Microcomputers I Fall B 2009 Lecture 3 Page 1 Lecture 3 Introduction to the Freescale 9S12 Purpose: Learn the major pieces of information about a new processor to look for in its technical documentation Discuss the information specific to the Freescale MC9S12DG256 microcontroller
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CE-320 Microcomputers I Fall B 2009 Lecture 3 Page 2 Register Set Also called the programming model , this shows the registers that may be used directly by the program and, to some degree, what operations may be performed on each register. In many processors, data may only be operated on if it is in a register, while some processors can perform limited operations on data that is still stored in memory. The diagram below shows the register set for the 9S12 family. 7 A 0 7 B 0 15 D 0 15 X 0 15 Y 0 15 S 0 15 PC 0 S X H I N Z V C CCR:
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CE-320 Microcomputers I Fall B 2009 Lecture 3 Page 3 Registers A: A one-byte (8-bit) general purpose register. Since many mathematical operations can be performed using A, it is also referred to as the A accumulator . B: A one-byte (8-bit) general purpose register. Since many mathematical operations can be performed using B, it is also referred to as the B accumulator . D: A two-byte (16-bit) general purpose register. The D register is actually the concatenation of the A and B registers. A is used as the more significant byte with B as the less significant byte. Note, the two bytes worth of registers may be used as either A and B or as D, but not both at the same time. X: A two-byte (16-bit) register primarily used to hold addresses. Y: A two-byte (16-bit) register primarily used to hold addresses. S:
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Lecture03_handout-F09 - CE-320 Microcomputers I Fall B 2009...

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