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Data strobe encoding
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<table><tbody><tr><td></td></tr><tr><td><i>Data strobe encoding and recovered clock.</i></td></tr></tbody></table> <p>Data strobe encoding (or D/S encoding) is an encoding scheme for transmitting data in <a href="/facts/Digital_circuit/vWgfC29C">digital circuits</a>. It uses two signal lines (e.g. wires in a cable or traces on a <a href="/facts/Printed_circuit_board/muSR2p43">printed circuit board</a>), <i>Data</i> and <i>Strobe</i>. These have the property that either Data or Strobe changes its <a href="/facts/Truth_value/SY4e2w8l">logical value</a> in one <a href="/facts/Clock_cycle/9UfTzGHx">clock cycle</a>, but never both. More precisely data is transmitted as-is and strobe changes its state if and only if data stays constant between two data bits. This allows for easy <a href="/facts/Clock_recovery/hrTr6rlS">clock recovery</a> with a good <a href="/facts/Jitter/UpLIJDVQ">jitter</a> tolerance by <a href="/facts/XOR/FHyr7hGQ">XORing</a> the two signal line values. </p><p>There is an equivalent way to specify the relationship between Data and Strobe. For even-numbered Data bits, Strobe is the opposite of Data. For odd-numbered Data bits, Strobe is the same as Data. From this definition it is more obvious that the XOR of Data and Strobe will yield a clock signal. Also, it specifies the simplest means of generating the Strobe signal for a given Data stream. </p><p>Data strobe encoding originated in <a href="/facts/IEEE_1355/0SdR2cbU">IEEE 1355</a> Standard and is used on the signal lines in <a href="/facts/SpaceWire/7LYsotsn">SpaceWire</a> and the <a href="/facts/FireWire/XYdQlxfy">IEEE 1394</a> (also known as <a href="/facts/FireWire_400/XYdQlxfy">FireWire 400</a>) system. </p><p><a href="/facts/Gray_code/HtbVlM7T">Gray code</a> is another code that always changes one logical value, but never more than one. </p>