What is the exact difference between a 74*374 and a 74*377? The first is classified as an octal edge triggered d-type flipflop while the latter is an 8-bit register. I don't understand the difference between them. Why would one use one over the other?

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    \$\begingroup\$ Have a look at the datasheets Google is that way ->. If you have a question about what in the datasheet is confusing you please come back and ask. \$\endgroup\$ – RoyC Apr 8 '17 at 10:53

374 has an output enable, you can make the outputs go high impedance

377 has a clock enable - you can tell the chip to ignore the clock.

  • \$\begingroup\$ I see, thank you for your answer. Is there a 7400 series IC readily available that has 8 d-type flipflops with both an output enable and a clock enable? \$\endgroup\$ – wich Apr 8 '17 at 19:56

As an addition to @Jasen's answer, the main reason behind setting the 74374 outputs to high impedance is to allow you to drive a bus line system without the need for any interface or pull-up components. In other words the high impedance feature allows you to use many 74374 chips with their outputs paralleled. This can not be applied with 74377 chips.

Look at the following picture which has been taken from this link.

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I would advice you as well to read the info provided in the already mentioned link.

  • \$\begingroup\$ Thank you for your answer. What is then the advantage of a 74*377 over a 74*374? To put it another way, when would one use a 74*377 instead of a 74*374? \$\endgroup\$ – wich Apr 8 '17 at 19:54
  • \$\begingroup\$ From the datasheets, you can find that 74377 has much more operating frequency (~125MHz) than 74374 (~35MHz). \$\endgroup\$ – Macit Apr 8 '17 at 20:34
  • \$\begingroup\$ Really? I don't see that difference in the TI datasheets for the HC variants. Are you perhaps looking at the 74AC377? \$\endgroup\$ – wich Apr 9 '17 at 7:51
  • \$\begingroup\$ TI datasheet SN74F377A \$\endgroup\$ – Macit Apr 9 '17 at 7:57

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