6. Configuring the Gateway
Field in the | Size in the | Description |
|
frame | frame |
| |
|
| ||
Checksum | 2 bytes | Error check type: Type of error check for the frame. | |
|
| - CRC | Default method. This is the method adopted for the Modbus |
|
| RTU protocol. |
|
|
| - LRC | This method relates to the Modbus ASCII protocol. So it |
|
| should not be used in this case. | |
|
| - XOR | Simple “OR Exclusive” applied to the frame’s bytes. |
|
| E.g. The LUFP9 gateway is specifically designed for the Modbus protocol RTU | |
|
| mode. The default value, “CRC”, should not be changed. | |
|
| Error check start byte: Indicates the number of the byte, in the frame, from | |
|
| which the calculation of the “checksum” should begin. The first byte in each | |
|
| frame carries the number 0. | |
|
| E.g. The calculation of a frame’s checksum should always begin with the first | |
|
| byte. The value of this field should therefore remain set to zero. | |
6.11.2.5. Configuring the Content of the Response Frame
The window shown below is obtained using “Edit Frame” from the “Response” menu. The values shown in it correspond to the values assigned by default to the Modbus command response we have created. The correspondence with the content of the corresponding Modbus frame has been added underneath this window.
Slave no.
Function no.
Word number (MSB / LSB)
Value of the word (MSB / LSB)
CRC16 (LSB / MSB)
Edit the values which are not greyed out, one after another.
There is a description of them on the next page, but also see the previous chapter, as the nature of the content of response frames is very similar to that of the fields in Modbus query frames.
If the value of a field from the response of a Modbus slave is different from that configured via AbcConf, the response will be rejected by the gateway. It will then proceed to a
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