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Hi, and new and I want to know what is the difference between command flags and control command in modbus communication
- Thread starter Joan HG
- Start date
Hello and welcome to the forum!
If you're new to Modbus, I recommend reading and understanding the following Modbus resources first:
https://control.com/technical-articles/introduction-to-modbus/
https://ipc2u.com/articles/knowledg...mple-with-detailed-descriptions-and-examples/
If this question is specifically how to interpret the Modbus tables for the DEIF AGC 200 genset controller (https://deif-cdn-umbraco.azureedge....4189341214_uk.xlsx?rnd=133578925210500000&v=9), take a look at the "Discrete output coil" and "Holding register" tabs in the Modbus tables spreadsheet for a definition of each of the command flags and control commands, respectively.
Note that it is common for Modbus vendors to expose the same data as both coils and as bits within holding registers (each holding register can contain up to 16 bits), which appears to be what this vendor has done (for example, Coil addresses 0 - 15 correspond to Holding Register address 5, bits 1 - 15). This is done as a convenience so the Modbus master device and/or integrator may choose which access method (coils or bits within holding registers) to use.
If you're new to Modbus, I recommend reading and understanding the following Modbus resources first:
https://control.com/technical-articles/introduction-to-modbus/
https://ipc2u.com/articles/knowledg...mple-with-detailed-descriptions-and-examples/
If this question is specifically how to interpret the Modbus tables for the DEIF AGC 200 genset controller (https://deif-cdn-umbraco.azureedge....4189341214_uk.xlsx?rnd=133578925210500000&v=9), take a look at the "Discrete output coil" and "Holding register" tabs in the Modbus tables spreadsheet for a definition of each of the command flags and control commands, respectively.
Note that it is common for Modbus vendors to expose the same data as both coils and as bits within holding registers (each holding register can contain up to 16 bits), which appears to be what this vendor has done (for example, Coil addresses 0 - 15 correspond to Holding Register address 5, bits 1 - 15). This is done as a convenience so the Modbus master device and/or integrator may choose which access method (coils or bits within holding registers) to use.
