Toho-electronics TTM200 Manuel d'utilisateur télécharger pdf (Page 23)

6.7 Example of CRC-16 calculations

Following is an example of calculating CRC-16 with VisualBasic6.0.

Variables are declared as shown below.

VisualBasic6.0 cannot use code-free variables. It therefore uses code-equipped 16-bit integer

variables as data. Similarly, the CRC calculation results are entered into code-equipped 32-bit

integer variables.

Dim CRC As Long

Dim i, j, arry_count As Integer

Dim c_next, c_carry As LongDim crc_arry(64) As Integer

Then enter calculable data into the crc_arry(), and enter the number of data items into the arry_count.

After that, run the following program to cause the calculation results to enter the CRC.

i = 0

CRC = 65535

For i = 0 To arry_count

c_next = crc_arry(i)

CRC = (CRC Xor c_next) And 65535

For j = 0 To 7

c_carry = CRC And 1

CRC = CRC ¥ 2

If c_carry Then

CRC = (CRC Xor &HA001) And 65535

End If

To affix an error code to the end of the message, affix first the low-level byte and then the high-level

byte of the CRC.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 50 51

Pas de commentaire

Toho-electronics TTM200 Manuel d'utilisateur Page 23