Category: I/O
Tool: Diamond/Radiant
Devices: MachXO2, MachXO3, ECP3, ECP5, CrossLink, CrossLinkPlus, CrossLink-NX, Certus-NX

First, I would like to make two points specific to Lattice.

[1] When using differential signals such as LVDS, use "T" (True=non-inverted) and "C" (Complementary=inverted) pairs (paired pins are determined for each device and package). increase).
[2] For differential signals, it is not necessary to specify the inverting input in the RTL description. Please specify by describing only the non-inverted side.

When performing pin placement, it is not necessary to specify the inversion side as in the RTL description, and only the non-inversion side is specified. The tool automatically assigns the reverse side to use the appropriate pin paired with it. Please note that an error will occur if you unintentionally assign some unrelated signal to the "C" pin that should be paired.

There are basically two ways to specify.

・For Diamond, open the "Spreadsheet View" (SSV), for Radiant, open the "Device Constraint Editor" (DCE), and specify the pin arrangement by entering the pin number in the "Pin" column. Also, select "LVDS" ("LVDS25" depending on the device) from the pull-down in the "IO_TYPE" column.
- SSV and DCE settings are written to text files. It has the extension .LPF (“Constraint File”) in Diamond and .pdc (“Post-Synthesis Constraint File”) in Radiant. It can also be specified by writing/editing LPF/pdc exported by SSV/DCE or already existing with a text editor. For details on the syntax for specifying pin assignments and I/O types, refer to the respective online help.