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Herry

Senior Member

Joined: 31/05/2014
Location: Australia
Posts: 261

Posted: 02:15pm 13 Apr 2017

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Hello all

I am desperately trying to find a table of pins to be strapped/earthed/etc. for the various divide possibilities of the 74HC390 (2,4,5,10,20,25,50,100). I cannot glean those from the datasheets (not being a genius). For example, I know from a Mr Carlson's Lab YouTube clip that for divide by 4 you strap 14 and 12, strap 15 and 3, input at 1, output at 13, strap 4,2,8,14,12 to earth. Where would I find the strappings for the other divisors?

Senior?! �Whatever it says, I'm a complete and utter beginner...

bigmik

Guru

Joined: 20/06/2011
Location: Australia
Posts: 2944

Posted: 05:34pm 13 Apr 2017

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Hi Herry,

From this Link which is a preview of an ebook available online.

Page 171 has these examples. for /50 /10 and /100

There is a bit of reading about the others but as it is your baby I am hand balling it back to you to read up on them..

Kind Regards,

Mick

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

Herry

Senior Member

Joined: 31/05/2014
Location: Australia
Posts: 261

Posted: 08:28pm 13 Apr 2017

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Thanks MIck

I was aware of that reference and it gives me two strappings. But my theoretical knowledge is not enough to extrapolate other strappings from the datasheet!

Senior?! �Whatever it says, I'm a complete and utter beginner...

CaptainBoing

Guru

Joined: 07/09/2016
Location: United Kingdom
Posts: 2137

Posted: 11:44pm 13 Apr 2017

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Hi Herry.

kind-of related... loads of the now defunct 74xx90 are still available as old new stock

here is a graphic I grabbed years ago which show how to do divide-by-any with it

http://www.fruitoftheshed.com/Circuit%20Ideas.7490-The-forgotten-divider.ashx

have a look for (74HC)4017 as well - it is a johnson ring counter but again can be made to divide by any really easily, I think it is largely forgotten but can be a really useful chip. The original 4017 CMOS was maxed out at around 1MhZ but the later 74 variants are good for 20Mhz

both of these are only a single decade though.Edited by CaptainBoing 2017-04-15

Herry

Senior Member

Joined: 31/05/2014
Location: Australia
Posts: 261

Posted: 01:08am 14 Apr 2017

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Thank you! Now that is exactly the kind of information I need for the 74HC390, or whatever succeeds it! I'd like to go fully up to date.

Senior?! �Whatever it says, I'm a complete and utter beginner...

vmazzo
Newbie

Joined: 15/02/2019
Location: Brazil
Posts: 1

Posted: 12:49pm 15 Feb 2019

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74HC390:

Divide by 2:
in: 1
out: 3
gnd: 2,4,8,12,14,15

Divide by 4:
in: 1
out: 13
12-14
3-15
gnd: 2,4,8,12,14

Divide by 5:
in: 4
out: 7
gnd: 1,2,8,12,14,15

Divide by 10:
in: 1
out: 7
3-4
gnd: 2,8,12,14,15

Divide by 20:
in: 1
out: 13
3-4
7-15
gnd: 2,8,12,14

Divide by 25:
in: 4
out: 9
7-12
gnd: 1,2,8,14,15

Divide by 50:
in: 12
out: 7
1-9
3-4
gnd: 2,8,14,15

Divide by 100:
in:12
out: 3
9-15
1-7
4-13
gnd: 2,4,8

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