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TomC
 Post subject: 74HCS series?
PostPosted: Tue Jul 06, 2021 7:52 pm 
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Has anyone looked at TI's new (as of 2019) 74HCS series for use as glue logic? A brief look at the docs indicates propagation delays between HC and AHC with somewhat lower power demand. HCS has no DIP packages, and functional variety that's broader than AHC but not so much as HC (note: I haven't looked over NXP's AHC portfolio).

Unless you need Schmidt trigger inputs I can't see why one would opt for HCS over AHC or HC. Or maybe I'm missing something?

74HCS family app note: https://www.ti.com/lit/scea069
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BigDumbDinosaur
 Post subject: Re: 74HCS series?
PostPosted: Wed Jul 07, 2021 2:22 am 
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TomC wrote:
Unless you need Schmidt trigger inputs I can't see why one would opt for HCS over AHC or HC. Or maybe I'm missing something?

The 74HCS family is targeted at noisy environments, such as machine controllers or automotive ECMs. Take out the Schmitt inputs and you have the 74HC family—essentially the same characteristics and performance. If you are intent on building a 6502 contraption that can run at double-digit clock speeds, neither 74HC or 74HCS would be the best choice for glue logic.

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GARTHWILSON
 Post subject: Re: 74HCS series?
PostPosted: Wed Jul 07, 2021 4:50 am 
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We don't need the Schmitt triggers for most glue logic; but having the option for other applications will make this family good to know about. It looks like the outputs are slightly stronger than 74HC, and the 74HCS00 is a little bit faster than the 74HC00, but nearly twice as fast as the 74HC132 which is the same thing with Schmitt-trigger inputs. The '139 appears to be a little less than twice as fast and the HC version. (These are the only two I compared.) 74AC generally seems to be about three times the speed of 74HC, but of course doesn't have the Schmitt-trigger inputs except on specific ones that always had it, like the '14 and '132.

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