Identification and Maintenance Functions (IMF)
IM Index Space and Partitions
In order to avoid conflicts with any PROFIBUS DP devices already installed in the field and to save address space for operational parameters, the I&M proposal follows the CALL_REQ service defined within IEC 61158-6.
This service, part of the "Load Domain" Upload/Download services, can be used within any module independent from any directory in a representative module (for example, slot 0) of a device. It uses index 255 within any slot and opens a separate addressable sub-index space. For I&M functions, the sub-index range from 65000 to 65199 is reserved. Sub-index blocks are called IM_Index.
The CALL_REQ service needs several header bytes, reducing the possible net data length to 236 bytes.
I&M0 - The Mandatory Record
The transport of the I&M parameters across the PROFIBUS DP network via MS1 (optional) or MS2 (mandatory) is supported. Only I&M0 data with IM0_Index = 65000 can be read. No other IM_Indices are supported.
During startup of the firmware this structure is initialized with the relevant information. A PROFIBUS DPV1 primary (master) (MS1 or MS2) can read this information at any time using the CALL_REQ mechanism.