data interface module added and tested

added files needed by the data_interface module
data interface module added and tested

Initial commit
Contains sub-modules sum_data_chk.vhd, test_data_gen.vhd and out_data_sel.vhd
Simply ties these modules together and to the opb_vdif_interface.vhd
data_interface module added and tested

Added signals required for interfacing to and testing data_interface
data_interface module added and tested

Initial commit
selects between normal data and one of two test signals:PRG and up-counter
data_interface module added and tested

Contains the logic to test input data against PRG
Contains the logic to acquire statistics of input data signals
data_interface module added and tested

Initial commit
Generates the internal PRN and counter test signals
Contains sub-module test_prg.vhd
data interface module added and tested

Initial commit
Generates a PRN sequence for the test_data_gen.vhd