10.6 Data Format Definition

10.6.3 Time Data Packets.

10.6.3.1 Time Data Packets, Format 0.

Reserved.

10.6.3.2 Time Data Packets, Format 1.

Time is treated like another data channel. If a time source other than "none" is used, the time packet will be generated at a minimum rate of 1000 milliseconds.

1. IRIG Time Type Formats. The 48-bit relative time counter shall be captured for insertion into the Time Packet Data header IAW IRIG 200 Serial Time Code Formats; On-Time Reference Marker definition.
2. All Non-IRIG Time Type Formats. The 48-bit relative time counter shall be captured for insertion into the Time Packet Data header at an integer multiple of 10 milliseconds.

   A Time Data Packet shall be the first dynamic data packet at the start of each recording. Only static Computer Generated Data packets may precede the Time Data Packet in the recording.

   If the Time Data Packet Source is None at least one Time Data Packet is required IAW the previous note.

   A packet with time data has the basic structure shown in Figure 10-15. Note that the width of the structure is not related to any number of bits. This drawing is merely to represent relative placement of data in the packet. Time Packets do not have Intra-Packet Headers.

   PACKET HEADER

   CHANNEL SPECIFIC DATA

   TIME DATA

   PACKET TRAILER

   Figure 10-15. General time data packet, format 1.

   Time Packet Channel Specific Data. The Packet Body portion of each Time Data Packet begins with a Channel Specific Data word formatted as shown in Figure 10-16a

   msb 31	12	11	8	7	4	3	lsb 0
   RESERVED		DATE		FMT		SRC
   Time Source (SRC). (bits 3-0) indicates the source of the time in the payload of each time packet. 0x0 = Internal (Time derived from the Clock in the Recorder) 0x1 = External (Time derived from a Clock not in the Recorder) 0x2 = Internal from RMM (Internal Time derived from the Clock in the RMM) 0x3 - 0xE = Reserved 0xF = None Time Format (FMT). (bits 7-4) indicate the Time Data Packet format. All bit patterns not used to define a time format type are reserved for future data type growth. 0x0 = IRIG-B 0x1 = IRIG-A 0x2 = IRIG-G 0x3 = Internal Real-Time Clock 0x4 = UTC Time from GPS 0x5 = Native GPS Time 0x6 thru 0xE = Reserved 0xF = None (time packet payload invalid) Date Format (DATE). (bits 11-8) indicate the Date format. All bit patterns not used to define a date format type are reserved for future growth. Bits 11-10: Reserved Bit 9: Indicates Date Format 0 = IRIG day available 1 = Month and Year available Bit 8: Indicates if this is a leap year 0 = Not a leap year 1 = Is a leap year Reserved. (bits 31-12) are reserved.

   Figure 10-16a. Time packet channel specific data format.

3. Time Packet Body. After the Channel Specific Data word, the time data words are inserted in the packet in Binary Coded Decimal (BCD) format as shown in Figure 10-16b and Figure 10-16c.

   msb 15		12		11		8		7		4		3		lsb 0
   0	TSn			Sn				Hmn				Tmn
   0	0	THn		Hn				0	TMn			Mn
   0	0	0	0	0	0	HDn		TDn				Dn

   Figure 10-16b. Time data - packet format, day format.

   msb 15		12		11		8		7		4		3		lsb 0
   0	TSn			Sn				Hmn				Tmn
   0	0	THn		Hn				0	TMn			Mn
   0	0	0	TOn	On				TDn				Dn
   0	0	OYn		HYn				TYn				Yn

   Figure 10-16c. Time data - packet format, day, month, and year format

   The following units of measure apply to Figure 10-16b and Figure 10-16c.

   Tmn	Tens of milliseconds	TDn	Tens of days
   Hmn	Hundreds of milliseconds	HDn	Hundreds of Days
   Sn	Units of seconds	On	Units of Months
   TSn	Tens of Seconds	TOn	Tens of Months
   Mn	Units of minutes	Yn	Units of Years
   TMn	Tens of minutes	TYn	Tens of Years
   Hn	Units of hours	HYn	Hundreds of Years
   THn	Tens of Hours	OYn	Thousands of Years
   Dn	Units of Days	0	Always zero

add a comment User Contributed Notes and Comments

Deprecated: Function strftime() is deprecated in /web/irig106/comments/show.inc on line 89

01/15/2007 23:11 - Bob (bob dot baggerman at gatech dot edu)

A note says "A Time Data Packet shall be the first dynamic data packet". I'm not sure exactly what constitutes a "Dynamic Data" packet. It would be nice if this were more specific.

Deprecated: Function strftime() is deprecated in /web/irig106/comments/show.inc on line 89

01/15/2007 23:08 - Bob (bob dot baggerman at gatech dot edu)

The spec doesn't explicitly specify when either time format from Figure 10-16b or Figure 10-16c. Format seems to come "Date format" but the wording isn't very specific. It would be clearer if the spec said "Bit 9, 0 = Use Figure 10-16b, 1 = Use Figure 10-16c.

Also, the bit fields for the Channel Specific Data are described from LSB to MSB, but Date Format description presents them MSB first. This turn around messed me up the first time I implemented time packets. It would be better if Date Format started with Bit 8.

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