CN102075290B - Aerial bus data coding and decoding methods - Google Patents

Abstract

The invention discloses an encoding and decoding method for aviation bus data. The encoding result is obtained after successively determining all attributes of the encoded data, determining the encoding value, setting intermediate data, and sequentially assigning values and symbol processing, and determining all the attributes of the data to be decoded sequentially. 1. Calculate the number of valid data bits to be decoded, calculate the maximum value of valid data bits before decoding, set the target code to be decoded and determine the data symbol to obtain the decoding result. The invention realizes a unified encoding and decoding method for various data, can set the data sign bit at any position of the data, and can set two data bits as the sign bit.

Description

A method for encoding and decoding aviation bus data

technical field

The invention relates to an encoding and decoding method.

Background technique

In modern aircraft, the transmission of bus information between various subsystems of the avionics system involves data encoding and decoding issues. In the process of data transmission, the source node needs to encode the original physical data into word/byte form that can be transmitted by the bus, and then reach the destination node through the bus transmission. The destination node needs to decode the data into the original physical quantity, which is convenient for users to operate. In the prior art, because the definition form of the interface control document (Interface Control Document, ICD) of different data transmission buses (such as ARINC429 bus, 1553B bus, RS232/422/485 bus) is different, the encoding and decoding methods of its data are also different. Differences, for example, for the transmission of 32-bit data, a 32-bit encoding and decoding system must be used, while for the transmission of 16-bit or 8-bit data, a 16-bit or 8-bit encoding and decoding method must be used. There is no unified standard, which leads to the poor versatility of the encoding and decoding methods, that is, different encoding and decoding methods are used for encoding and decoding data with different digits. In addition, in the existing encoding and decoding methods, the sign bit of the data can generally only be set at the highest bit, which lacks flexibility and is not convenient for data integration.

Contents of the invention

In order to overcome the poor reusability and inflexible deficiencies of the prior art, the present invention provides a general aviation bus data encoding/decoding method and its realization, which can complete 32-bit (ARINC429 data), 16-bit (1553B data) and 8-bit ( RS232/422/485 data) encoding/decoding, at the same time, this method can encode the sign bit at any position of the data, and can set multiple data bits as the sign bit.

The technical solution adopted by the present invention to solve its technical problems is as follows.

The encoding method includes the following steps:

Step 1. Determine all attributes of the data to be encoded. According to ICD, these attributes include the highest effective value of the coded data is D _h , the lowest bit is D _l , the lowest bit weight is Q, and the symbol matrix (the data symbol matrix is represented by m_GEZ and m_LTZ, which is a 32-bit integer, where The symbol matrix m_GEZ is always 0x00000000. If the data is a signed number and the D _i bit is a sign bit, then the D _i bit corresponding to the symbol matrix m_LTZ is 1, and the other bits are all 0; if the data is an unsigned number, the symbol matrix m_LTZ is 0x00000000), the maximum value of data m_Max, and the minimum value of data m_Min.

Step 2. Determine the value of the data to be encoded. Suppose the data to be encoded is a floating-point number v, if v is greater than or equal to m_Max, then v is taken as m_Max; if v is less than or equal to m_Min, then v is taken as m_Min; if v is between m_Max and m_Min, then v remains unchanged .

Step 3. Set v1, v2, v3, v4, and S1 as intermediate variables, which are double words. Considering the rounding error of the computer system, the following precision algorithm is adopted: when v is a non-negative number, assign (v/Q+0.5) to v1 after rounding; when v is a negative number, take (v/Q-0.5) Assign it to v1 after adjustment.

Step 4, first shift 1L (representing an unsigned long integer 0x00000001) to the left by D _l bits, multiply the obtained result with v1 and then assign it to v2, and calculate the number of effective data bits nBits and nBits occupied by the encoded data at the same time = _Dh - _Dl +1. Further, calculate the maximum value of the valid data bits after encoding, and shift it to the left by D _l , and the result is a double-word Mask, that is, Mask=((1L<<nBits)-1)<<D _l , and then v2 and Mask performs an AND operation, and assigns the result to v3.

Step five, symbol processing. Perform XOR operation with m_GEZ and m_LTZ, and assign the result to the double word Sign. When v is a non-negative number, perform an AND operation with Sign and m_GEZ, and assign the result to S1; when v is a negative number, perform an AND operation with Sign and m_LTZ, and assign the result to S1. Finally, perform an OR operation on v3 and S1, and assign the result to v4.

Step 6. The v4 data is the encoding result.

The decoding method includes the following steps:

Step 1. Determine all attributes of the data to be decoded. According to ICD, these attributes include the highest effective value of the decoded data is D _h , the lowest bit is D _l , the lowest bit weight is Q, and the symbol matrix (the data symbol matrix is represented by m_GEZ and m_LTZ, which is a 32-bit integer, where The symbol matrix m_GEZ is always 0x00000000. If the data is a signed number and the D _i bit is a sign bit, then the D _i bit corresponding to the symbol matrix m_LTZ is 1, and the other bits are all 0; if the data is an unsigned number, the symbol matrix m_LTZ is 0x00000000), the maximum value of data m_Max, and the minimum value of data m_Min.

Step 2: Calculate the number of effective data bits nBits=D _h −D _l +1 to be decoded.

Step 3: Calculate the maximum value Mask of valid data bits before decoding, that is, Mask=(1I<<nBits)-1.

Step 4: Set the target code to be decoded as dw, shift dw to the right by D1 _bits , AND the result with Mask, the result is v1, then multiply v1 by Q, and assign the result to v2.

Step five, determine the data symbol. Perform XOR operation with m_GEZ and m_LTZ, assign the result to the double word Sign, then perform AND operation with dw and Sign, the result is Sign1.

Step 6. If Sign1 is equal to m_LTZ, take v2 as the opposite number, that is, v=-v2, otherwise v=v2.

Step 7, v is the decoding result.

The beneficial effects of the present invention are: in the transmission process of aviation bus data, according to the ICD definition of avionics system, by setting different data bits of symbol matrix, various data (including 32-bit ARINC429 data, 16-bit 1553B data and 8-bit RS422/485 data) are encoded and decoded, and a unified encoding and decoding method is realized. In its available field, a kind of encoding and decoding standard can be formed, and the present invention can set the data sign bit at any position of the data. position, and two data bits can be set as the sign bit (in ARINC429 data, some use two data bits as the sign bit; in 1553B bus and RS422/485 data, one data bit is generally used as the sign bit) , which cannot be realized in traditional encoding and decoding algorithms, and this advantage is also realized by m_GEZ and m_LTZ, that is, if the sign bit is set in the D _i bit of the data, only the corresponding position of m_LTZ is set to 1. For example, if the sign bit is set to the highest bit D ₁₅ , you only need to assign 0x8000 to m_LTZ; if you set the sign bit to D ₁₁ , you only need to assign 0x0800 to m_LTZ.

Below in conjunction with embodiment the present invention is further described.

Detailed ways

(1) The encoding and decoding implementation of 16-bit 1553B data with one sign bit is as described in Example 1 and Example 2.

Method embodiment 1:

Suppose the original data to be encoded is v=60 (assuming that v represents the absolute height of the target point, which is 16-bit 1553B bus data to be encoded).

Step 1: Determine the attributes of the encoded data. According to ICD, the highest bit of data encoding is D _h =14, the lowest bit is D _l =0, the lowest bit weight is Q=0.25, and the symbol matrix of the data (m_GEZ is 0x0000 , m_LTZ is 0x8000, that is, the sign bit is set at the highest bit D ₁₅ ), the maximum value of the data is m_Max=2 ¹⁵ -1, and the minimum value is m_Min=-2 ¹⁵ .

Step 2: Since v is between the maximum value m_Max and the minimum value m_Min, v does not change.

The third step: v=60>0, so v1=v/Q+0.5, considering computer rounding error, then v1=240.

Step 4: v2=v1*(1L<<0)=(240) _D =(00F0) _H , nBits=14-0+1=15. Mask=0x7FFF, v3=v2&Mask=0x00F0.

Step 5: Sign=m_GEZ^m_LTZ=0x8000. Since v>0, S1=Sign&m_GEZ=0x0000. v4=v3|S1=0x00F0.

Step 6: 0x00F0 is the encoding result.

Similarly, the encoding result of -60 can be calculated as 0xFF10.

Method embodiment 2:

Now decode "0x00F0".

The first step: determine the attribute of the coded data, this step is the same as the first step in embodiment 1.

The second step: nBits=14-0+1=15.

Step 3: Mask=(1L<<15)-1=0x7FFF.

Step 4: v1=(dw>>0)&Mask=(0x00F0) _H =(240) _D , v2=v1*Q=60.

Step 5: Sign=m_GEZ^m_LTZ=0x8000. Sign1=dw&Sign=0x0000.

Step 6: Since Sign1 is not equal to m_LTZ, v=v2=60.

Step 7: 60 is the decoding result.

(2) The encoding and decoding implementation of 32-bit ARINC429 data with two sign bits is as described in Example 3 and Example 4.

Method embodiment 3:

Suppose the original data to be encoded is v=100 (assuming that v represents the true air speed of the carrier aircraft, which is the 32-bit ARINC429 bus data to be encoded).

Step 1: For a double word with 32 bits of encoded data, according to ICD, the attributes of encoded data are: the highest bit of data encoding is D ₂₉ , the lowest bit of data encoding is D ₀ , and the lowest bit weight of data is Q= 0.25. The symbol matrix of the data (m_GEZ=0x00000000, m_LTZ=0xC0000000), the maximum value of the data is m_Max=2 ³⁰ -1, and the minimum value of the data is m_Min=-2 ³⁰ .

Step 2: Since v is between the maximum value and the minimum value, v=100 does not change.

The third step: because v>0, so v1=v/Q+0.5, considering the rounding error of the computer, then v1=400.

Step 4: v2=v1*(1L<<0)=0x00000190, nBits=29-0+1=30. Mask=0x3FFFFFFF, v3=v2&Mask=0x00000190.

Step 5: Sign=m_GEZ^m_LTZ=0xC0000000. Since v>0, S1=Sign&m_GEZ=0x00000000. v4=v3|S1=0x00000190.

Step 6: 0x00000190 is the encoding result.

Method embodiment 4:

Now decode "0x00000190".

The first step: determine the attribute of the encoded data, this step is the same as the first step in embodiment 3.

The second step: nBits=29-0+1=30.

Step 3: Mask=(1L<<30)-1=0x3FFFFFFF.

Step 4: v1=(dw>>0)&Mask=(0x00000190) _H =(400) _D , v2=v1*Q=100.

Step 5: Sign=m_GEZ^m_LTZ=0xC0000000. Sign1=dw&Sign=0x00000000.

Step 6: Since Sign1 is not equal to m_LTZ, v=v2=100.

Step 7: 100 is the decoding result.

Claims (2)

1. the coding method of an aviation bus data is characterized in that comprising the steps:

Step 1, determine all properties of data to be encoded, comprise that the effective value highest order of data is D behind the coding _h, lowest order is D _l, the lowest order weights are the maximum m_Max of Q, sign matrix, data, the minimum value m_Min of data; Sign matrix represents with m_GEZ and m_LTZ, is 32 integers, and wherein sign matrix m_GEZ perseverance is 0x00000000, if data are signed number, and D _iThe position is sign bit, the D that then symbol matrix m_LTZ is corresponding _iThe position is 1, and other positions are 0 entirely; If data are unsigned number, then symbol matrix m_LTZ is 0x00000000;

Step 2, determine the numerical value of data to be encoded, establishing data to be encoded is floating number v, if v more than or equal to m_Max, then v is taken as m_Max; If v is less than or equal to m_Min, then v is taken as m_Min; If v at m_Max and m_Min between the two, then v is constant;

Step 3, establish v1, v2, v3, v4, S1 is intermediate variable, and is double word; When v is nonnegative number, be assigned to v1 after (v/Q+0.5) rounded; When v is negative, be assigned to v1 after (v/Q-0.5) rounded;

Step 4, first the 1L D that moves to left _lThe position, the result that obtains and v1 multiplied each other is assigned to v2 again, calculates simultaneously the afterwards shared valid data figure place nBits of data of coding, nBits=D _h-D _l+ 1; The maximum of valid data position behind the calculation code, and with its D that moves to left _lThe position, acquired results is double word Mask, namely Mask=((1L＜＜nBits)-1)＜＜D _l, then v2 and Mask are done and computing, acquired results is assigned to v3;

Step 5, m_GEZ and m_LTZ are made XOR, the result is assigned to double word Sign; When v is nonnegative number, Sign and m_GEZ are done and computing, the result is assigned to S1; When v is negative, Sign and m_LTZ are done and computing, the result is assigned to S1; At last v3 and S1 are made exclusive disjunction, and the result is assigned to v4;

Step 6, v4 data are coding result.

2. the coding/decoding method of an aviation bus data is characterized in that comprising the steps:

Step 1, determine all properties of data to be decoded, comprise that the effective value highest order of data is D after the decoding _h, lowest order is D _l, the lowest order weights are the maximum m_Max of Q, sign matrix, data, the minimum value m_Min of data; The data symbol matrix represents with m_GEZ and m_LTZ, is 32 integers, and wherein sign matrix m_GEZ perseverance is 0x00000000; If data are signed number, and D _iThe position is sign bit, and the Di position that then symbol matrix m_LTZ is corresponding is 1, and other positions are 0 entirely; If data are unsigned number, then symbol matrix m_LTZ is 0x00000000;

Step 2, calculating need the valid data figure place nBits=D of decoding _h-D _l+ 1;

Step 3, calculate the maximum Mask of valid data position before the decoding, namely Mask=(1L＜＜nBits)-1;

Step 4, to establish object code to be decoded be dw, the dw Dl position that moves to right, acquired results and Mask done and computing, and the result is v1, and then v1 multiply by Q, and the result is assigned to v2;

Step 5, specified data symbol are done XOR to m_GEZ and m_LTZ, and its result is assigned to double word Sign, then dw and Sign are done and computing, and the result is Sign1;

If step 6 Sign1 equates that with m_LTZ then v2 being taken as opposite number is v=-v2, otherwise v=v2;

Step 7, v are decoded result.