Hi Xiang,<br>
<br>
The MSO4 does not have one single option for protocol analysis, instead it has over a dozen protocol analysis packs to choose from, depending on the protocols you wish to analyze. You can see them all in the "Upgrades" section of the product's page: <a href="https://www.tek.com/en/products/oscilloscopes/4-series-mso">https://www.tek.com/en/products/oscilloscopes/4-series-mso</a> <br>
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If you wish to see which licenses are already on your instrument, then you can do so by going into "Help", "About" and checking your "Installed Options".<br>
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In the same link you should be able to request a quote, which will include buying instructions.