The PAC-Designer I2C utility for the POWR1220AT8 device will work with the Lattice USB Download cable when using the WindowsXP operating system. It will not work with Windows7 operating system at this time.
This utility was created so that a user could connect to a special connector on the POWR1228AT8 Evaluation Board and communicate with the device over the I2C connection. On this board there was special circuitry added to convert the JTAG cable unidirectional data lines, TDI and TDO, to the bidirectional SDA data line for I2C. Please see the schematic drawing that shows the initial implementation of the special circuitry on the POWR1220AT8 evaluation board.
This can be found in Application Note AN6065 which is available at the following web link: AN6065 - ispPAC-POWR1220AT8 Evaluation Board