Alternate Tap Positions

Here are some selected alternate tap positions which can be used with cascaded 8-bit shift registers used in the fibonacci configuration to obtain a maximal length sequence. These are suitable for shift register IC's where outputs of registers 6, 7, and 8 of each circuit are available. Cases with 2 and with 4 taps are shown. (This list is not complete.)

No. IC'sNo. Registers
used		Taps Cycles before
repeat		Approx Repeat Time
for 100kHz Clock
176, 71271.27 ms
2158, 1532767328 ms
21514, 1532767328 ms
32017, 201,048,57510 s
3228, 14, 15, 224,194,30342 s
32314, 238,388,60784 s
32315, 16, 22, 238,388,60784 s
32314, 15, 22, 238,388,60784 s
3237, 14, 22, 238,388,60784 s
3237, 8, 22, 238,388,60784 s
3247, 22, 23, 2416,777,215168 s
3247, 16, 22, 2416,777,215168 s
3247, 8, 22, 2416,777,215168 s
3246, 7, 22, 2416,777,215168 s
43124, 312,147,483,6476 hr
43116, 24, 30, 312,147,483,6476 hr
4318, 16, 24, 312,147,483,6476 hr
4317, 22, 24, 312,147,483,6476 hr
4318, 23, 24, 312,147,483,6476 hr
43216, 23, 30, 324,294,967,29511.9 hr
4326, 15, 30, 324,294,967,29511.9 hr
43214, 23, 30, 324,294,967,29511.9 hr
75531, 5536,028,797,018,963,96711,400 yr
86362, 639,223,372,036,854,775,8072.9 mill yr
107970, 79 604,462,909,807,314,587,353,0872 x 1011 yr
1310394, 10310,141,204,801,825,835,
211,973,625,643,007		3.2 x 1018 yr
15119111, 119664,613,997,892,457,936,
451,903,530,140,172,287		2.1 x 1023 yr
16127126, 127170,141,183,460,469,231,
731,687,303,715,884,105,727		5.4 x 1025 yr
20159128, 159730,750,818,665,451,459,101,842,
416,358,141,509,827,966,271,487		2.3 x 1035 yr



Applicable Shift Registers include: 4014, 4021
Other Shift Registers which can be used include: 74164, 74595, 74599, 4094
(Though additional circuitry may be necessary.)
The current best estimate of the age of the universe is 13.8 x 109 yr.

Questions/Comments to: suits@mtu.edu

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