------------------------------------------------------------- STAGES LENGTH FEEDBACK 2 3 1,2 3 7 2,3 4 15 3,4 5 31 3,5 6 63 5,6 7 127 6,7 8 255 4,5,6,8 9 511 5,9 10 1,023 7,10 11 2,047 9,11 12 4,095 6,8,11,12 13 8,191 9,11,12,13 14 16,383 4,8,13,14 15 32,767 14,15 16 65,535 4,13,15,16 17 134,071 14,17 18 262,143 11,18 19 524,287 14,17,18,19 20 1,048,575 17,20 21 2,097,151 19,21 22 4,194,303 21,22 23 8,366,607 16,23 24 16,777,215 17,22,23,24 25 33,554,431 22,25 26 67,108,863 20,24,25,26 27 134,217,727 22,25,26,27 28 268,435,455 25 28 29 536,870,911 27,29 30 1,073,741,823 7,26,29,30 31 2,147,483,647 26,31 MAGIC FEEDBACK connections for pseudorandom sequences. It two feedback numbers are shown, you XOR (exclusive-or) them together. If four numbers are shown, you xor by pairs and then XOR the two intermediate results. Either hardware or software may be used. __ 86 xor / //_________________________________________ _______/ || | | \ ||_________________________________ | | \_\\ 573 flipflops | | | ___ ___ ___ ___ ___ | ___ | |__|D Q|____|D Q|____|D Q|____|D Q|____|D Q|__|_|D Q|_| | | | | | | | | | | | | _\|C | _\|C | _\|C | _\|C | _\|C | _\|C | | /|___| | /|___| | /|___| | /|___| | /|___| | /|___| |________|________|________|________|________| six stage pseudorandom sequence generator produces 63 sixbit binary numbers in apparently random , yet exactly repeating order