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Programming FCs (Functions) and FBs for S7 Ethernet CPs

151

SIMATIC NET NCM S7 for Industrial Ethernet

C79000-G8976-C129–06

Working with the Job Header

Free UDP connections require a job header in the user data area.

The following schematic illustrates the structure of the job buffer and the meaning

and location of the parameters in the job header.

Job header

User data

User data area

Job buffer

(high byte)EB

(low byte)

Data byte 2041Data byte 2040

Bytes 0,1

Bytes 2,3

Bytes 4,5

Bytes

2046,2047

Data byte 1Data byte 0

Bytes 6,7

Port

IP address

Figure 5-1 Sending and Receiving on a Free UDP Connection with Programmed Addresses

S In the picture (entries in hexadecimal) the following IP address is assumed:

142.11.40.35 (example only);

S For the port address 1003, the following would be entered: for low byte: EB

;

for high byte: 03

S The user data area can be up to 2048 bytes long. Up to 2042 bytes of user data

can be transferred. 6 bytes are reserved for the job header.

Please note that the data length specified in the block call (LEN parameter)

must include the header and the user data!

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Siemens S7 Bedienungsanleitung Seite 151