Gray code

[′grā ‚kōd] (communications) A modified binary code in which sequential numbers are represented by expressions that differ only in one bit, to minimize errors. Also known as reflective binary code.

Gray code

(hardware)A binary sequence with the property that only onebit changes between any two consecutive elements (the twocodes have a Hamming distance of one).

The Gray code originated when digital logic circuits werebuilt from vacuum tubes and electromechanical relays.Counters generated tremendous power demands and noise spikeswhen many bits changed at once. E.g. when incrementing aregister containing 11111111, the back-EMF from the relays'collapsing magnetic fields required copious noise suppression.Using Gray code counters, any increment or decrement changedonly one bit, regardless of the size of the number.

Gray code can also be used to convert the angular position ofa disk to digital form. A radial line of sensors reads thecode off the surface of the disk and if the disk is half-waybetween two positions each sensor might read its bit from bothpositions at once but since only one bit differs between thetwo, the value read is guaranteed to be one of the two validvalues rather than some third (invalid) combination (aglitch).

One possible algorithm for generating a Gray code sequenceis to toggle the lowest numbered bit that results in a newcode each time. Here is a four bit Gray code sequencegenerated in this way:

0 0 0 00 0 0 10 0 1 10 0 1 00 1 1 00 1 1 10 1 0 10 1 0 01 1 0 01 1 0 11 1 1 11 1 1 01 0 1 01 0 1 11 0 0 11 0 0 0

The codes were patented in 1953 by Frank Gray, a Bell Labsresearcher.

http://nist.gov/dads/HTML/graycode.html.

Gray code

A binary code used to represent digits generated from a mechanical sensor that may be prone to error. Used in telegraphy in the late 1800s, and also known as "reflected binary code," Gray code was patented by Bell Labs researcher Frank Gray in 1947.

Only Change One Bit
In Gray code, there is only one bit location different between numeric increments, which makes mechanical transitions from one digit to the next less error prone. The following chart shows normal binary representations from 1 to 10 and the corresponding Gray code.

Decimal Binary Gray Digit Code Code 0 0000 0000 1 0001 0001 2 0010 0011 3 0011 0010 4 0100 0110 5 0101 0111 6 0110 0101 7 0111 0100 8 1000 1100 9 1001 1101 10 1010 1111

单词	gray code
释义	Gray code Gray code n (Computer Science) a modification of a number system, esp a binary code, in which any adjacent pair of numbers, in counting order, differ in their digits at one position only, the absolute difference being the value 1 [named after Frank Gray, 20th-century American physicist] Gray code Gray code [′grā ‚kōd] (communications) A modified binary code in which sequential numbers are represented by expressions that differ only in one bit, to minimize errors. Also known as reflective binary code. Gray code (hardware)A binary sequence with the property that only onebit changes between any two consecutive elements (the twocodes have a Hamming distance of one). The Gray code originated when digital logic circuits werebuilt from vacuum tubes and electromechanical relays.Counters generated tremendous power demands and noise spikeswhen many bits changed at once. E.g. when incrementing aregister containing 11111111, the back-EMF from the relays'collapsing magnetic fields required copious noise suppression.Using Gray code counters, any increment or decrement changedonly one bit, regardless of the size of the number. Gray code can also be used to convert the angular position ofa disk to digital form. A radial line of sensors reads thecode off the surface of the disk and if the disk is half-waybetween two positions each sensor might read its bit from bothpositions at once but since only one bit differs between thetwo, the value read is guaranteed to be one of the two validvalues rather than some third (invalid) combination (aglitch). One possible algorithm for generating a Gray code sequenceis to toggle the lowest numbered bit that results in a newcode each time. Here is a four bit Gray code sequencegenerated in this way: 0 0 0 00 0 0 10 0 1 10 0 1 00 1 1 00 1 1 10 1 0 10 1 0 01 1 0 01 1 0 11 1 1 11 1 1 01 0 1 01 0 1 11 0 0 11 0 0 0 The codes were patented in 1953 by Frank Gray, a Bell Labsresearcher. http://nist.gov/dads/HTML/graycode.html. Gray code A binary code used to represent digits generated from a mechanical sensor that may be prone to error. Used in telegraphy in the late 1800s, and also known as "reflected binary code," Gray code was patented by Bell Labs researcher Frank Gray in 1947. Only Change One Bit In Gray code, there is only one bit location different between numeric increments, which makes mechanical transitions from one digit to the next less error prone. The following chart shows normal binary representations from 1 to 10 and the corresponding Gray code. Decimal Binary Gray Digit Code Code 0 0000 0000 1 0001 0001 2 0010 0011 3 0011 0010 4 0100 0110 5 0101 0111 6 0110 0101 7 0111 0100 8 1000 1100 9 1001 1101 10 1010 1111
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