[ibis-macro] Question about clock_times
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx>
- Date: Wed, 27 Jan 2010 21:43:59 -0800
Hello AMI experts,
I just noticed something in the AMI portion of the official IBIS v5
specification.
Section 3.2.2.3 clock_times is not labeled as optional, yet the text
implies that this is only applicable to Rx models. Note the words
"clock recovery loop" towards the end:
| 3.2.2.3 clock_times
|
| Vector to return clock times. The clock times are referenced to the
start
| of the simulation (the first AMI_GetWave call). The time is always
| greater or equal to zero. The last clock is indicated by putting a
value
| of -1 at the end of clocks for the current wave sample. The clock_time
| vector is allocated by the EDA platform and is guaranteed to be
greater
| than the number of clocks expected during the AMI_GetWave call. The
clock
| times are the times at which clock signal at the output of the clock
| recovery loop crosses the logic threshold. It is to be assumed that
the
| input data signal is sampled at exactly one half clock period after a
| clock time.
A Tx model would not have a clock recovery loop, so I would think that
a Tx GetWave function would not return anything in clock_times. Is the
EDA tool still required to allocate memory for clock_times even for Tx?
Also note that the spec doesn't spell out exactly how much memory the
EDA
tool needs to allocate, only that it should be "greater than the number
of clocks expected". Since we have seen crashes due to a DLL wanting to
write more clock_times than what we "expected" from it, and the safest
thing to do would be to allocate as much memory as the number of
simulated
bits, this seems to be quite a waste if we had to allocate the same
amount
of memory to a Tx model's clock_times also...
Isn't there a better way of doing this?
Thanks,
Arpad
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