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74hc595

Brian MillerBrian Miller Posts: 25
edited 2004-09-22 14:31 in BASIC Stamp
How·many 74HC595 chip can be chained together?

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Newbie, using the NX-1000 24/40 Board with a BS2p40

Comments

  • DonDon Posts: 34
    edited 2004-09-22 05:25
    Many.· How many do you want to connect?· The only issue will be the load on the clock and any other common signals.· Even so, it is a simple matter to·clock groups of '595s using separate parallel drivers.

    With regard to this, there is a concept called "fan out" which specifies how many inputs a given output can drive.· If it is not·specified on a particular datasheet, you can calculate it by finding the values for the input high and low currents and the output source and sink capabilities.· Then divide the latter by the former to find the maximum number of inputs that can be driven.· Generally, you wouldn't want to load the outputs to the maximum.· Rather, it is best to leave a little margin for good measure.

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    Don Kinzer

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  • Brian MillerBrian Miller Posts: 25
    edited 2004-09-22 14:31
    Thanks, that makes sense.

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    Newbie, using the NX-1000 24/40 Board with a BS2p40
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