IRIGB_对时信号.pdf

IRIG-B Time Code IRIG-B Time Code Although the synchronization bus can carry many forms of time signal, the IRIG-B time code is the most widely used synchronization signal within substations. The basic form of IRIG-B consists of a pulse-width modulated digital data stream at the rate of 100 pulses per second. The leading edge of each pulse is precisely positioned in time on the incremental 10mS point within the second, while the pulse width modulation conveys time and date information repeating within each 100 pulse frame i.e. once per second. There are a number of variations of IRIG-B time codes in common use. IRIG-B time codes are defined using a 4-character descriptor: B x y z, and x, y and z have meaning as follows: B x y z [format] [modulation type] [frequency/resolution] [coded expression] B denotes IRIG-B x designator, modulation type has three possible values: 0 = Unmodulated, also called DC level shift 1 = Amplitude Modulated (AM) sine wave 2 = Modified Manchester modulated The y designator, frequency/resolution has values as follows: 0 = no carrier / index count interval (commonly used with IRIG-B) 1 = 100Hz carrier (not used with IRIG-B) 2 = 1000Hz carrier (commonly used with IRIG-B) The z designator, coded expression has values as follows: 0 = BCD, CF, SBS 1 = BCD, CF 2 = BCD 3 = BCD, SBS BCD = Binary Coded Decimal format = basic time-of-year information (does not include year information). CF = Control Function = additional information including year information (eg IEEE1344 extensions or AFNOR extensions). SBS = Straight Binary Seconds = seconds-of-day in binary format. The valid combinations in use for IRIG-B are: B00z, B12z and B22z. B00z (DC level-shift IRIG-B) B00z (DC level-shift IRIG-B) has been favored fo