Irig-b Coded---GPS timing

First, the Irig serial timecode format Introduction:

Irig-b is a per-second frame of the serial timecode, the total width of each code element is 10ms, a time frame period consists of 100 code elements for pulse width coding. Each code element has 3 code types: binary 0, 1, and positional identifiers. Divided into 3 field codes: The 1th field is year (year, day, hour, minute, second), the 2nd is the Control function number field, and the 3rd is the time information in the day that is represented by the binary seconds symbol, which loops 1 times every 24 hours. The "punctual" reference point of the code element is its pulse frontier, the reference mark of the frame is composed of a position identification sign and a neighboring reference code element, the pulse width is 8ms; each 10 code element has a position identification mark, so 1 seconds a total of 10 position identification signs, namely: P1,p2,p3,...,p9,p0, They are 8ms pulse width, PR is frame reference point, and the pulse widths of binary "1" and "0" are 5ms and 2ms respectively.

Second, Irig-b code:

Frame structure: Start flag, seconds (digit), separator flag, seconds (10 digits), Datum mark, minute (single digit), dividing mark, minute (10 digit), Datum mark, time (digit), separating mark, time (10 digits), Datum mark, Day of the year starting from the New Year (digit), separating Mark, Day (10), Datum mark, Day (hundred) (the previous number is BCD), 7 control codes (defined in a special use case), the number of seconds since the start of the day 0 o'clock (for pure binary integers), and the end flag.

code element recognition

code element: each pulse in the time format is called a code element. The "On time" reference point of the code element is its pulse frontier, and the repetition rate of the code element is called the code element rate. The code element rate of B code is 100pps.

index count: Each code element corresponds to an index count. The time interval between two adjacent code elements is the index count interval, and the index count interval for b yards is 10ms. The index count starts at "0" at the frame reference point and increments by 1 for each index count interval until the frame ends. The index count interval for b yards per frame is 100, and the index count number is from 0~99 until the frame ends.

position Identification mark: the width of the position identification mark is the 0.8,B code of the index count interval of the code is 8ms. Position identification mark the forefront of the P0 at the frame reference point (that is, PR) at an index count interval, after each 10 code element has a position recognition flag, respectively, P1, P2......,P9 position identification flag Repeat rate of one-tenth of the code element rate. The B-yard is 10pps.

code Word: All the time formats are pulse-width codes. The pulse widths of the binary "1" and "0" are 0.5 and 02, respectively, of the index count interval. The B-code binary "1" and "0" have a pulse width of 5ms and 2ms respectively.

reference mark: The reference mark of the time frame is made up of a positional identification mark (P0) and an adjacent reference code element (PR). The width of the reference code element is 0.8 of the corresponding time code index count interval. The B-yard is 8ms. The time frame's "on time" reference point is the forefront of the reference code element.

when frame: a time format frame reference flag starts. Consists of all the code elements between the two adjacent frame reference markers. The time frame's repetition rate is the frame rate, and its period is the frame period. The B-code has a frame rate of 1/s, while the frame period is 1 seconds.

It is a frame per second, each code element width is 10ms, one time frame period consists of 100 yards.

A time format frame starts from the frame reference flag, so that two consecutive 8ms wide pulses represent the start of the second, if the code element is encoded from the second 8ms, respectively, 0,1,2, ... 99 yards, in the B-code time format contains days, seconds and minutes. Time series is seconds-minutes-hours-days. The information bits occupied are 7 bits per second, 7 bits, 6 bits, and 10 bits per day. The position is between p0~p5. P6~P0 contains additional control information.

Second: 1,2,3,4,6,7,8 code element;

Sub: 10,11,12,13,15,16,17 code element;

Time: 20,21,22,23,25,26,27 code element;

Index flag: Section 5,14,24, 34 yards.

Tod Time: use 80, 81, 82, 83, 84, 85, 86, 87, 88, 90, 91, 92 , 93, 94, 95, 96, 97 a total of 17 code elements

Third, B-code decoder design scheme (software design method)

Decoding the B code is to extract the time, minute and second information contained in B code and convert it into a form that can be recognized by the computer. The key of decoding is to detect the high-level width of each code element in B code, first to detect the location of two consecutive 8ms wide code elements, and then detect the subsequent 30 code element pulse width, to determine the time, minutes, seconds. detection of high-level width: The B-code into the INT0 end of the microcontroller, the INT0 pin from low to high, start the microcontroller's internal timer T0, start counting: At the INT0 pin from high to low (that is, falling edge), Triggers a INT0 interrupt, reads the value of the counter, the pulse width equals the count value multiplied by the count cycle.

Iv. Reference Documents:

Http://blog.chinaunix.net/uid-26694208-id-4059940.html

Http://www.360doc.com/content/10/1121/23/2253845_71297575.shtml

Http://zhidao.baidu.com/question/301515557.html

Http://baike.baidu.com/link?url=N2DaD3Douabtr4W-L_A5UWAPQfCM5T0vq9kWp4

Http://www.cnblogs.com/TFH-FPGA/p/3169915.html

Http://wenku.baidu.com/link?url=IgLZIvBuIjm8F_ ioxk5rvpbvehfa7t8lralcsh7qmcullsvtpeeacxivrwtxco8zmvt1cunnw7icp0fdyoji14sxweh0h6mt6xvyio5dl0k

Http://wenku.baidu.com/view/cecfc759f111f18583d05ae0.html?re=view

Http://wenku.baidu.com/view/87f9b02ce2bd960590c67712.html?re=view

Irig-b Coded---GPS timing