Embedded Systems Design - March 2008 - (Page 33) 0308esd.p33to37 2/13/08 7:59 PM Page 33 feature You can implement the cyclic redundancy check function in an embedded systems design with minimal impact on memory or performance by using linear feedback shift register instructions more intelligently. CRCminimal memory calculation with BY YANIV SAPIR AND YOSEF STEIN Efficient lmost every form of digital information exchange can introduce communication errors. Sometimes, these errors can be ignored (for example, an erroneous pixel in a high-resolution video is merely unnoticeable). However, most of the time, they cannot be ignored, and we want to ensure that the receiver gets an absolutely correct stream of information. In order to overcome the inherent inaccuracy of information transmission, a few methods for error detection and correction have been developed. Generally speaking, these methods introduce some redundancy to the actual message, which in turn can be used to detect errors and in some cases to recover the original data. One of the most common methods is the use of the CRC (cyclic redundancy check) function, a family of codes commonly used to ensure data integrity in digital data streams by detecting errors due to noise or dropouts of bits in the message stream. The CRC calculates a series of bits (also commonly referred to as a CRC) that is appended to the data stream and transmitted along with the message. The receiver performs a CRC function on the message and compares the result with the received CRC code to verify the integrity of the message. CRC is commonly used in a number of applications such as digital communications and computer data storage systems. The CRC is performed through binary polynomial division between the transmitted message and a polynomial divisor and is usually implemented using a linear feedback shift register (LFSR). An LFSR is a shift register where its next state is a linear combination of its previous state and input bits. In our context, the linear operators A footprint www.embedded.com | embedded systems design | MARCH 2008 33 http://www.embedded.com
Table of Contents Feed for the Digital Edition of Embedded Systems Design - March 2008 Embedded Systems Design - March 2008 Contents #Include Programming Pointers Designing DSP-based Motor Control Using Fuzzy Logic Hardware/Software Verification Enters the Atomic Age Efficient CRC Calculation with Minimal Memory Footprint Programming Your Own Microcontroller Advertising Index Break Points Marketplace Embedded Systems Design - March 2008 Embedded Systems Design - March 2008 - (Page BB1) Embedded Systems Design - March 2008 - (Page BB2) Embedded Systems Design - March 2008 - Embedded Systems Design - March 2008 (Page Cover1) Embedded Systems Design - March 2008 - Embedded Systems Design - March 2008 (Page Cover2) Embedded Systems Design - March 2008 - Embedded Systems Design - March 2008 (Page 1) Embedded Systems Design - March 2008 - Embedded Systems Design - March 2008 (Page 2) Embedded Systems Design - March 2008 - Contents (Page 3) Embedded Systems Design - March 2008 - #Include (Page 4) Embedded Systems Design - March 2008 - #Include (Page 5) Embedded Systems Design - March 2008 - #Include (Page 6) Embedded Systems Design - March 2008 - #Include (Page 7) Embedded Systems Design - March 2008 - #Include (Page 8) Embedded Systems Design - March 2008 - Programming Pointers (Page 9) Embedded Systems Design - March 2008 - Programming Pointers (Page 10) Embedded Systems Design - March 2008 - Programming Pointers (Page 11) Embedded Systems Design - March 2008 - Programming Pointers (Page 12) Embedded Systems Design - March 2008 - Programming Pointers (Page 13) Embedded Systems Design - March 2008 - Programming Pointers (Page 14) Embedded Systems Design - March 2008 - Programming Pointers (Page 15) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 16) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 17) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 18) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 19) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 20) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 21) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 22) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 23) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 24) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 25) Embedded Systems Design - March 2008 - Designing DSP-based Motor Control Using Fuzzy Logic (Page 26) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 27) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 28) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 29) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 30) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 31) Embedded Systems Design - March 2008 - Hardware/Software Verification Enters the Atomic Age (Page 32) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 33) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 34) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 35) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 36) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 37) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 38) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 39) Embedded Systems Design - March 2008 - Efficient CRC Calculation with Minimal Memory Footprint (Page 40) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 41) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 42) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 43) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 44) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 45) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 46) Embedded Systems Design - March 2008 - Programming Your Own Microcontroller (Page 47) Embedded Systems Design - March 2008 - Advertising Index (Page 48) Embedded Systems Design - March 2008 - Break Points (Page 49) Embedded Systems Design - March 2008 - Break Points (Page 50) Embedded Systems Design - March 2008 - Marketplace (Page 51) Embedded Systems Design - March 2008 - Marketplace (Page 52) Embedded Systems Design - March 2008 - Marketplace (Page Cover3) Embedded Systems Design - March 2008 - Marketplace (Page Cover4)
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