There are several properties used to define differential pairs in the
CSV file:
- Signal Name
- DiffPair Signal
- DiffPair Type
- I/O Standard
The other values in the CSV file are used to validate a diff pair, to ensure they are fully compatible, but they are not used to define the pair. You can define differential pairs in the CSV file in the following ways:
- Diff Pair
- This is a direct definition of the two signals which make up a differential pair. Two port entries each have DiffPair Signal values linking to the Signal Name of the other and have complementary DiffPair Type values, one N and one P. The tool checks to ensure that the other properties such as I/O Standard are compatible when forming the diff pair.
- Single-Link Diff Pair
- Two port entries with complementary DiffPair Type values (one N, one P), but only one port has a DiffPair Signal linking to the other Signal Name. The tool creates the differential pair if all other properties are compatible.
- Single Port Diff Pair
- A single port entry with a differential I/O Standard, a DiffPair Type value, and a DiffPair Signal that does not otherwise appear in the CSV file. The tool creates the opposite side of the differential pair (the N or P side) with all properties matching those on the original port.
- Inferred Diff Pair
- Two ports entries with differential pair I/O standards (for example, DIFF_HSTL, DIFF_SSTL) and Signal Names that infer the N and P side. The tool infers a differential pair if all other properties are compatible.