ECC SECDED: flip a bit, watch the syndrome find it, flip two

An 8-bit byte as a 13-bit SECDED word. Flip any bit: the syndrome names it and it is fixed. Flip two: detected, not fixed.

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Where the numbers come from

gHashTag/t27 specs/fpga/secded.t27 (t27#8931): every value on the page is its fn bodies, compiled to wasm (logic.js), with 6 tests over every byte, every single flip and every double flip of three words
R. W. Hamming, Error Detecting and Error Correcting Codes, Bell System Technical Journal 29(2), 1950; the extended (SECDED) form used per word by ECC memory