Pre-Scaled Counter Example

• Highest speed is required in the pre-scaled block

  • Constrain the two counter blocks separately to avoid over-constraining COUNT12

• Define two groups for use in TIMESPEC.

  • Example UCF file:

INST FFS(PRE2) TNM = PRE;

INST COUNT12 TNM = UPPER;

TIMESPEC TS_PRE = FROM PRE TO PRE 60 MHZ;

TIMESPEC TS_TC2CE = FROM PRE TO UPPER 60 MHZ;

TIMESPEC TS_UPPER = FROM UPPER TO UPPER 15 MHZ;

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