Материал: m012900e

Fieldbus controller 750-842 • 57

Example of process input image

3.2.4.1Example of a process input image

The following figure is an example of a process input image. The configuration comprises of 16 digital and 8 analog inputs.

The process image thus has a data length of 8 words for the analog and 1 word for the digital inputs, i.e. 9 words in total.

0x000C %IX8.12 0x000D %IX8.13 0x000E %IX8.14 0x000F %IX8.15

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58 • Fieldbus controller 750-842

Example of process output image

3.2.4.2Example of a process output image

The following example for the process output image comprises of 2 digital and 4 analog outputs.

It comprises of 4 words for the analog and 1 word for the digital outputs, , i.e. 5 words in total.

In addition, output data can be read back with an offset of 200hex (0x0200) added to the MODBUS address.

DO: Digital Output

AO: Analog Output

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Fieldbus controller 750-842 • 59

Process data architecture for MODBUS/TCP

3.2.4.3Process data architecture for MODBUS/TCP

For some bus modules or their variations, the process data architecture is specific for the fieldbus controller used.

In the case of the ETHERNET controller with MODBUS/TCP the control/status byte is always masked in addition to the data bytes. This is required for the two-directional data exchange of the bus module with the higherranking control system. The control byte is transmitted from the control system to the module and the status byte from the module to the control system. This allows, for example, the display of overshooting or undershooting of the area.

Attention

Please refer to the respective bus module description in Chapter 4 "I/O modules" for the specific architecture of the respective control/status byte.

The following shows the representation of some selected modules in the process image.

In the examples, the order in which the modules are physically arranged in the node reflects the order in the image table starting with register address 0x0000. If the module is located at any other position in the fieldbus node, the process data of all previous byte-wise oriented modules have to be taken into account. In the process image, this results in a basic register address for the module. To address its process data words, the quoted offset is added to this basic address.

If an analog input or output module is added, it takes up 2 x 16 Bit input or output data.

With the ETHERNET fieldbus controller with MODBUS/TCP the process image is organized word-by-word (word-alignment) and the control/status byte is always a low byte.

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60 • Fieldbus controller 750-842

Process data architecture for MODBUS/TCP

3.2.4.3.1 750-404, /000-00X Counter modules

This process data architecture holds true for the counter modules 750-404, 750-404/000-001, 750-404/000-002 and 750–404/000-004.

The data format of the counter modules five bytes is mapped out by the module as four data bytes and one additional control/status byte. The module supplies a 32 bit counter-output, while occupying 3 words each in the process image with word-alignment.

The input bytes D0 to D3 form the 32 bit counter-output.

In the output bytes D0 to D3 the initial value of the counter can be set.

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Fieldbus controller 750-842 • 61

Process data architecture for MODBUS/TCP

3.2.4.3.2 750-404/000-005 2 Channel Up Counter 16 Bit

The data format of the counter modules five bytes is mapped out by the module as four data bytes and one additional control/status byte, while occupying 3 words each with word-alignment.

The input bytes D0 and D1 form the 16 bit reading of counter 1 and the input bytes D2 and D3 form the 16 bit reading of counter 2.

When setting the counter, the load value of counter 1 is transferred in the output bytes D0 and D1. The load value of counter 2 is transferred respectively in the output bytes D2 and D3.

3.2.4.3.3 750-511, /000-002 2-Channel Digital Pulsewidth module

This process data architecture holds true for the 2 Channel Pulsewidth modules 750-511 and 750–511/000-002.

Item-No.: Description:

The process image of the 750-511 and 750-511/000-002 appears with 6 bytes of input and 6 bytes of output data, while occupying 4 words each in the process image with word-alignment.

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