Communicating Applications Spec - Get diagnostics results

        Entry:
          AX = CB13h
          DL = 00h
        Return:
          AX = 0040h in progress
             > 0   passed
             < 0   failure code

        Note: diagnostics return values are hardware dependent

        Intel Connection CoProcessor failure codes:
                bit 3: 9600 bps FAX modem module failed
                bit 2: SDLC chip failed
                bit 1: RAM failed
                bit 0: ROM checksum failed