Uses 2 cycles each to set the shift and xor mask registers. It has 3 operation modes: normal shift,
After reset, set the shift register and xor state, after that normal shift mode
| # | Input | Output |
|---|---|---|
| 0 | clock | output[0] lsb normal lfsr output |
| 1 | reset | output[1] other 7 bits to see the full state |
| 2 | mode[0] 00 normal shift mode, 01 set register mode, | output[2] |
| 3 | mode[1] 10 set mode registers, 11 unused | output[3] |
| 4 | data_in[0] is used for both filling register and xor mask state | output[4] |
| 5 | data_in[1] needs 2 cycles to fill all 8 bits | output[5] |
| 6 | data_in[2] first cyle is lower 4 bits, 2nd upper 4 bits | output[6] |
| 7 | data_in[3] see above | output[7] |