Siemens SIMATIC S5 Manual page 65

S5-95U, SINEC L2
An FMA request consists of an 8-byte header. The confirmation, depending on the service,
consists of a maximum of 58 bytes. Bytes 0 to 7 are assigned to the confirmation header; the
requested data start with byte 8.
Figure 3-8 shows the structure of a service request and of a confirmation. The designations in the
header blocks are taken from the PROFIBUS Standards.
The FMA headers contain the following parameters. Not all parameters are completely evaluated for
all functions.
Service Request
Byte
0 com_class
FMA_Request=00
(service request)
1 user_id
Freely assignable ID. That ID is returned
unchanged in the confirmation.
2 service_code
Type of service requested
3
irrelevant
4
irrelevant
5
irrelevant
6 rem_add_station*
Address of destination station
(hexadecimal)
7
irrelevant
* Required only by FMA service FDL_STATUS
Figure 3-8. Structure of the FMA Headers for Request and Confirmation
Storing the Request Header and the Confirmation Data
Store the transmit data and the received data in the flag area or the data area.
The maximum length of the confirmation (header + data) is 58 bytes. Because of the rather large
maximum amount of data contained in a confirmation, we recommend choosing only the data area.
We also recommend storing request and confirmation in the same data block.
EWA 4NEB 812 6112-02
H
Start-Up, Tests, and Diagnostics
Confirmation
Byte
0 com_class
FMA_Confirmation=01
(acknowledgment from firmware
following FMA_Request)
1 user_id
ID assigned in the FMA_Request
2 service_code
Type of service provided by the
layer 2 firmware
3 link_status
OK message, or error message; indicates
the success or failure of the previous
service request
4
irrelevant
5
irrelevant
6 rem_add_station*
Address of destination station
(hexadecimal)
7
irrelevant
8
. . Data
.
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