JTAG is a standard test interface defined by the Joint Test Action Group and supported on many late-model digital receivers for factory test purposes. Operating using a six-wire interface and a personal computer, the JTAG interface was originally intended to provide a means to test and debug embedded hardware and software. In the satellite TV world, JTAG is most often used to obtain read-write access to nonvolatile memory within a digital receiver; initially programs such as Wall and JKeys were used to read
box keys from receivers with embedded CAMs but JTAG has since proven its legitimate worth to satellite TV fans as a repair tool to fix receivers where the firmware (in flash memory) has been corrupted.