1 / 27

Today’s Lecture

Embedded System Spring, 2011 Lecture 10: Arithmetic, Logic Instruction and Programs Eng. Wazen M. Shbair. Today’s Lecture. Arithmetic Instructions Signed Number Concepts and Arithmetic Operations Logic and Compare Instructions. Arithmetic Instructions.

angie
Download Presentation

Today’s Lecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Embedded SystemSpring, 2011Lecture 10: Arithmetic, Logic Instruction and Programs Eng. Wazen M. Shbair

  2. Today’s Lecture • Arithmetic Instructions • Signed Number Concepts and Arithmetic Operations • Logic and Compare Instructions IUG- Embedded System

  3. Arithmetic Instructions • Unsigned numbers are defined as data in which all the bits are used to represent data (no bits are set aside for neg. or pos. sign). • Addition of unsigned numbers • ADDLW k • ADDWF fileReg, d, a • ADDWFC (adding two 16-bit numbers) • What happens to flag register?

  4. Addition of unsigned numbers

  5. ADDWFC & addition of 16 bit number • When adding two 16-bit data operand, we need to be concerned with the propagation of a carry form lower byte to higher byte. • Multi byte addition vs. individual byte addition ??

  6. ADDWFC

  7. BCD Number System • We use the digits 0 to 9 in everyday • Binary Coded Decimal (BCD) • Unpacked BCD • The lower 4 bits is just used • Requires 1 byte • Ex. (0000 0010) • Packed BCD • A single byte has two BCD numbers • Efficient in storing data • Ex. ( 0101 0010)

  8. BCD Number System • What is the result if you add 0x17 0x28 0x3F This is not BCD number To convert it to BCD add 6 The result will be : 45

  9. DAW, Decimal Adjust WREG • Works only with WREG • Add 6 to the lower or higher nibble if needed. • After execution • If the lower nibble is greater than 9, or if DC = 1, add 0110 to the lower nibble. • If the upper nibble is greater than 9, or if C =1, add 0110 to the upper nibble. • Doesn’t require the use of arithmetic instructions prior the DAW execution.

  10. DAW, Decimal Adjust WREG

  11. DAW, Decimal Adjust WREG

  12. Subtraction of unsigned numbers • Subtracter circuit is cumbersome. (Why?) • PIC performs the 2’s complement then uses adder circuit to the result. • Take one Clock Cycle. • There are four sub instructions • SUBLW k (k – WREG) • SUBWF f d ( destination = fileReg – WREG) • SUBWFB (subtract with borrow ) • SUBFWB (subtract with borrow )

  13. Subtraction of unsigned numbers

  14. Multiplication of unsigned number • PIC supports byte-by-byte multiplication • One of the operand must be in WREG and the other operand is literal K value. • After multiplication, the result is stored in SFR registers PRODH and PRODL (16 bit)

  15. Division of unsigned numbers • There is no single instruction for the division of byte/byte numbers. • You need to write a program. • Repeated subtraction • The numerator is place in a fileReg • Denominator is subtracted from it repeatedly • The quotient is the number of times we subtracted • The reminder is in fileReg upon completion

  16. Example

  17. Signed Number and Arithmetic Operations • The Most Significant Bit (MSB) is set aside for the sign (+ or -) (0 for positive & 1 for negative) • The rest, 7 bits, are used for the magnitude. • To convert any 7-bit positive number to negative use the 2’s complement.

  18. Signed Number • You have 128 negative numbers and 127 positive numbers

  19. Signed Number

  20. Logic and Compare Instructions • Widely used instructions • ANDLW k • ANDFW FileReg, d • IORLW k • IORFW FileReg, d • XORLW k • XORFW FileReg, d • Effect only Z and N Flags

  21. Example

  22. Complement Instructions • COMF FileReg,d • Takes the 1’s complement of a file register • Effect only Z and N Flags • NEGF FileReg • Takes the 2’s complement of a file register • Effect all Flags

  23. Compare Instructions

  24. Compare Instructions

  25. References • Jie Hu , ECE692 Embedded Computing Systems , Fall 2010. • PIC Microcontroller And Embedded Systems: using Assembly and C for PIC 18, M. Mazidi, R. McKinlay and D. Causey, Prentice Fall, 2008. • Eng. Husam Alzaq, Embedded System Course, IUG, 2010 IUG- Embedded System 27

More Related