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The pins are
not available as differential pairs for EP3C55, if the pin-out file is correct.
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Ahh yes, I think I see the problem.
In the EPC380, J18/K18 are paired. However in the EP3C55, J18/K18 are both available as IO but are rebundled with other DIFFIO pairs. K18 is paired with pin K17 and J18 is only a single-ended IO (its diff pair being only available in the larger package). The T4/T5 pair is a similar situation.
I see now that moving to the larger devices requires more VCC and GND pins and so sometimes the DIFFIO pairs are broken up and used for this. I wasn't expecting the pairs to get rebundled - as was the case here.
I think I can conclude that the migration view within Pin Planner definitely is not wrong but it is also not complete since it showed these pins available across all three devices but does not indicate that their differential pairing may change or be lost.
Thanks FvM.
-A
Honored Contributor
