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Another question: you say that the specifications for toggle rate for each I/O standard are in the device handbook. But I have search in the stratix II gx handbook and I didn't found them ?!
Could you tell me in which chapter / section have you find theses informations.
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Volume 1, Section I, Chapter 4, under "Maximum Input and Output Clock Toggle Rate". Find the correct table for output clock rate (these tables apply to outputs with regular data signals, not just clocks), change the stated frequency to period with picosecond resolution, and adjust by the derating factor in Table 4-97.