Scribd
Upload
224 views7 pages

Error Corection

Uploaded by

Athalla Study
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF or read online on Scribd
224 views7 pages

Error Corection

Uploaded by

Athalla Study
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF or read online on Scribd
You are on page 1/ 7
ERROR DETECTION AND CORRECTION CODES = 95 [EBTRA error DETECTION AND CORRECTION CODES In this section, two methods for adding bits to codes to either detect a single-bit error or detect and correct a single-bit error are discussed. The parity method of error detection is. introduced, and the Hamming method of single-error detection and correction is covered. ‘When a bit in a given code word is found to be in error, it ean be corrected by simply inverting it. After completing this section, you should be able to = Determine if there isan error in a code based on the party bit ® Assign the proper patity bit toa code = Use the Hamming code for single-error detection and correction = Assign the proper party bits for single-error correction "Parity Method for Error Detection ‘Many systems use a parity bit as a means for bit error detection. Any group of bits contain either an even or an odd number of Is. A parity bitis attached to a group of bits to make the total number of Is in a group always even or always odd, An even parity bit makes the to- tal number of Is even, and an odd parity bit makes the total odd. A given system operates with even or odd parity, but not both. For instance, if a system ‘operates with even parity, a check is made on each group of bits received to make sure the total number of Is in that group is even. If there is an odd number of 1s, an error has occurred. Asan illustration of how parity bits are attached toa code, Table 2-10 lists the parity bits for each BCD number for both even and odd parity. The parity bit for each BCD number is in the P column, 0 ‘Third parity check: | Bit P, checks positions 4, 5, 6, and 7. ‘There is one 1 in this group. Parity check is bad, 1 (MB) Result: ‘The error position code is 100 (binary four). This says that the bitin position 4 isin error, Ibis a 0 and should be a 1, The corrected code is 0011001, which agrees with the transmitted code. | Related Problem Repeat the process illustrated in the example ifthe received code is 0111001. ERROR DETECTION AND CORRECTION CODES = 101 EXAMPLE 2. a I I saad ‘The code 101101010 is received, Correct any errors. There are four party bits, and ‘odd parity is used. Solution First, make a bit position table like Table 2-15, TABLE 2-15 | BIT DESIGNATION Phare Pienaar Ons. Fa eG a EO ort | 0100 | 0101 | 0110 | 0111 | 1000 | 1001 Received code First parity check Bit P, checks positions 1, 3,5, 7, and 9. ‘There are two Is in this group. Parity check is bad, ———___________, 1q.sp) Second parity check: Bit P, checks positions 2, 3, 6, and 7. ‘There are two 1s in this group. Parity cheek is bad,§ 1 Third parity check: Bit P, checks positions 4, 5, 6, and 7. ‘There are two 1s in this group. Parity check is bad, ——_________, | Fourth parity check Bit P, checks positions 8 and 9. ‘There is one 1 in this group. Party check is good, ———_________ oqwsp) Result: ‘The error position code is 0111 (binary seven). This says thatthe bitin position 7 is in error. The corrected code is therefore 101101110. Related Problem The code 101111001 is received. Correct any error if odd parity is used. [ener Ce ae REVIEW 1, Which odd-parity code i in error? (2) 1011 (b) 1110 (e) 0101 (4) 1000 2. Which even-party code iin error? (a) 11000110 (b) 00101000 (e) 10101010 () 11111011, | 3. Add an even parity bt to the end of each ofthe following codes. | (a) 1010100 (b) 0100000 (c) 1110111 (A) 1000110 4. How many part bits are required for data bits 11010 using the Hamming code? 5. Create the Hamming code for the data bits 0011 using even parity.

You might also like