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Altera_Forum
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15 years ago

DDR2 pin placement Cyclone 3 HPC II

Trying to meet the (absurdly tight) layout requirements for (32 DQ) DDR2 ram on Cyclone 3. HPC II. The layout engineer keeps trying to move pins (within the x8 DQ groups) and the resulting pin map ...
Altera_Forum's avatar
Altera_Forum
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15 years ago

"Critical warning: Fitter could not properly route signals from DQ I/Os to DQ capture registers because the DQ capture registers are not placed next to their corresponding DQ I/Os"

Maybe not fatal, but not something to blindly push past, either.

EP3C120F484I7

dq23 = A18

dq22 = A16

dq21 = D19

dq20 = F15

dq19 = E15

dq18 = E16

dq17 = C17

dq16 = C19

dm2 = A17

ds2 = F13

If I swap A17 and A18, the fault goes away, which is surprising because it is actually A16 that is preferred for DM2.

There are other swaps that cause this fault, but I don't have the data. Some of the other issues I've seen are now understood as our error.