Technical data

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Fig. 7 shows the integration of the GSD file and the parameterisation by the example of a

Siemens S7 SPC:

Fig.7 S7 Hardware configuration

Explanations of Fig. 7:

1 Profibus address of the slave device (here 2, for example), this address must

correspond to the address entered in the DK900.

2+3 Data channel selected (here the process data channel, for example)

4 Input address (here 200..208 = 9 Bytes, for example)

5 DP identifier, the hexadecimal identifier 0x98 of the process data channel is

displayed as 152 (decimal) in this example. This identifier is a description of the

data structure and contains, among others, information on data length, the number of

consistent bytes, and data flow direction.

4.3.3. Consistent reading and writing

Data that belong together with respect to their contents and must therefore not be

separated are called consistent data. For example, the actual value of the DK900 and the

status always belong together and must not be adulterated by reading them out at different

points in time. Therefore, the DK900 always generates a consistency over all data bytes

transmitted.

If a Siemens S7 SPC is used, it is generally impossible to access the device via load

instructions that access the individual bytes or words of the periphery and/or process

image of the inputs, for example, since the data area is consistent over its entire length.

In order to have an S7 communicate with one/several DK900(s), the following system

functions must be used:

· SFC 13 "DPNRM_DG" Read the slave diagnosis

· SFC 14 "DPRD_DAT" Read the consistent data of a DP standard slave

· SFC 15 "DPWR_DAT" Consistently write data to a DP standard slave

The above stated system functions are included in the scope of supply of Step7 (Version

V5.), they can be found in the Standard Library, and are described in the Step7 Reference

Manual.

DK900 10