Setup and hold time margins

Hithesh

How are setup and hold time margins calculated?

I design Analog mostly, but now I have my hands on digital systems. I was not able to find a good description on google.

Any books or app notes?

over 14 years ago

0 Chris Cockrill over 14 years ago

TI__Mastermind 46480 points

Setup and hold times are not calculated they are actually measured. The area between the setup and the hold times is where you would not want the clock to change if you expect the output to be effected. Here is an appnote with some explaination.

http://focus.ti.com/lit/an/szza036b/szza036b.pdf

0 Hithesh over 14 years ago in reply to Chris Cockrill

Genius 3290 points

Already read that. What about setup and hold skew?

0 Chris Cockrill over 14 years ago in reply to Hithesh

TI__Mastermind 46480 points

There are no setup an hold time skews. They are tested so that if you stay within the limits the part should work correctly across temp and process. Although there may be some skew on actual setup and hold times, you should not have any signal changing in this area if you go by the datasheet limits.

0 Farida Rajkotwala over 14 years ago in reply to Chris Cockrill

TI__Prodigy 10 points

Are there several methods to measure setup and hold time?

For example: to measure input setup and hold with respect to clock, do we move data rising edge independent of data falling edge.

Is the setup time measured by moving the window or only the edge from left to right?

Similarly measure hold time from moving the second data edge from right to left while keeping edge one fixed?

0 Chris Cockrill over 14 years ago in reply to Farida Rajkotwala

TI__Mastermind 46480 points

Setup and hold time are measured by moving the edge of the data in reference to the clock until you see a fail.

Logic

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Setup and hold time margins