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port output timestamp

Posted: Fri Mar 23, 2018 6:37 pm
by aelder
If I run this

Code: Select all


out buffered port:32 p_4bit_out = XS1_PORT_4A;

p_4bit_out <: 0 @ t0;
p_4bit_out <: 0 @ t1;
p_4bit_out <: 0 @ t2;
printf("\n Three back-to-back writes to p_4bit_out give timestamp deltas of %d and %d\n", t1 - t0, t2 - t1);
in the simulator (set to xCORE-200 eXplorer) I observe
Three back-to-back writes to p_4bit_out give timestamp deltas of 9 and 9
Why is the time delta 9 instead of 8?

Re: port output timestamp

Posted: Fri Mar 23, 2018 9:27 pm
by mon2
Guessing that the extra cycle is to perform the actual timestamp itself. You could confirm this by reviewing the disassembly of this source code, with and without the timestamp option to see the difference.

https://www.xmos.com/published/how-disa ... g-xobjdump