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Appendix A. Advanced Topics – Spectronics
Appendix A.1. Default Data Types
When a Spectronics address range is specified, a particular Data Type is implied. The defaults are as follows:
Address range |
| Data_Type | Function Code (Write) | Function Code (Read) |
40001 - 49999 |
| Register | 16 | 3 |
30001 - 39999 |
| Analog _Input | n/a. | 4 |
10001 - 19999 |
| Digital_Input | n/a. | 2 |
00001 - 09999 |
| Coil | 15 | 1 |
Appendix A.2. | Single Writes |
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When writing the default data types can be overwritten using the “Single_Coil” and “Single_Register” settings as part of the Map Descriptor configuration. In that case the Function codes for writes will be as follows:
Address range | Data_Type | Function Code (Write) |
40001 - 49999 | Single_Register | 6 |
30001 - 39999 | Coil | 5. |
Example: FC 6 = Write Single Register
Add a parameter to the Spectronics client side Map Descriptor called Data_Type.
If you specify the Data_Type as Single_Register and the Function as WRBC or WRBX, then a Spectronics poll with FC 6 will be generated.
Of course Single_Register implies a length of one, and even if you try to set the length longer in the csv file, the length is limited to 1 in the driver.
Appendix A.3. Write-Thru Operation
Consider a client Map Descriptor that is configured to read data using a FC 3 (Read Multiple Register) operation. It is now possible do a write thru operation on the existing Client Map Descriptor by storing data to the Client Map Descriptors Data Array.
The Write Cache Map Descriptor that is created will use the following function codes depending on the Cache Map Descriptor Length and the Clients Node Type.
Single Register Write - FC 6 - When the length of the Cache Map Descriptor is one. This will normally be the case.
Multiple Register Write – FC 16 - When the length of the Cache Map Descriptor is larger than one or the Node_Type has been set to “Block_Mode”.
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