Technical data

Storing the request header and confirmation data
The data to be transferred (8 bytes) and the received data (max. 250 bytes)
should be stored in a data block. Correct storage of the header information
in a DB (see Fig. 12.4) is necessary for error-free use of an FMA service. It
is advisable to provide enough space for the confirmation data in the same
DB.
Note
The following rules apply to FMA services:
➣
If parameters occupy two bytes (one word) the order in which these
bytes are stored in the data word of a data block is important:
– left data (DL): low byte of the parameter
– right data (DR): high byte of the parameter.
The header bytes are explained as necessary in the service descriptions
starting in Section 12.3.
The program example is described in detail for the FMA service
FDL_READ_VALUE. Setting up the DB is also illustrated as
comprehensively as the user program.
The user program for the other FMA services has an analogous structure.
The only difference is that a different DB must be called with parameters
assigned for the particular service (e.g. service_code).
Service and Diagnostics using FMA Functions B8976060/02
Volume 1 12 - 8