What does negative setup and hold values mean?

[mohammed.peer]

I have seen negative values for setup time and hold time, but whether it is possible to have negative value for time?? then what does that mean???

 

[rberek]

You can have negative setup and hold time requirements for a device.

For example, if you have a negative setup time requirement, the data may arrive at the pins of the device after the relevant clock edge arrives at the pins and the data will still be sampled correctly. This means that internal to the device, the clock experiences a larger delay relative to the data, so that when they both arrive at the internal circuitry that samples the data, the data arrives before the clock signal does.

A similar situation holds true for negative hold time, except that the data is delayed more than the clock.

r.b.

 

[Iouri]

negative set up time usually means your design does not meet timing constrains. negative hold time it is pretty common since data is latching on the next clock

 

[mohammed.peer]

negative set up time usually means your design does not meet timing constrains. negative hold time it is pretty common since data is latching on the next clock

Hi,
I was talking about specifications i.e. you can find negative setup or hold time in specifications itself. And you might be talking about slack, that must always be positive for a circuit to give proper response. anyways thanks for ur reply.