SN74HCS74: Not understanding datasheet: Setup time before CLK high

Klaas-Jan Winkel

Prodigy 60 points

Part Number: SN74HCS74

Tool/software:

Hi,

In the datasheet it it mentions two Tsu (setup time) specifications, 1 for data and one for PRE/CLR inactive.

Does that mean the first one is DATA + pre/clr active cq low?

And the second one DATA + pre/clr inactive.

To put it more simply, if pre and clr are high/inactive, what is the setup time for 2V?

And i am running at 3V so how to calculate it for 3V?

Thanks in advance!

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 327310 points

If you violate the data setup time, then the resulting output might be the previous data value.
If you violate the /PRE/CLR setup time, then the resulting output might still be affected by /PRE or /CLR, and the clocked data might get lost.

See [FAQ] What are the performance specifications of the HCS logic family at 3.3V operation?

Logic

Logic forum

SN74HCS74: Not understanding datasheet: Setup time before CLK high