Siemens SIMATIC S5 Manual page 57

S5-95U, SINEC L2
Operating the Programmable Controller with a SINEC L2 Interface
Figure 3-2 shows the operating principle of a programmable controller with the SINEC L2 interface.
Programmable controller
Control
processor
Operating
system
STEP 5 user
program
(OB, PB, FB, SB)
STEP 5 data
elements (DBs,
flags)
Figure 3-2. Operating Principle of an S5-95U with the SINEC L2 Interface
Communications Processor
The communications processor handles the frame traffic via the SINEC L2 network in parallel with
the control processor.
The communications processor has the following tasks:
• Receive frames that are used for network management, e.g., token frames, via SINEC L2
- Interpret the frame
- Trigger adequate reactions
• Receive frames that contain data via SINEC L2
- Interpret the frame
- Store the data in STEP 5 data elements
• Transmit frames that are used for network management, e.g., token frames, via SINEC L2
• Transmit frames that contain data via SINEC L2
- retrieve the data from STEP 5 data elements
- pack the data into frames and transmit
SINEC L2 Interface
9-pin subminiature D female connector as specified in the PROFIBUS Standards .
Internally
assigned
RXD/TXD (A) (data line A)
Not assigned
P 5V2 (supply
voltage+)
Figure 3-3. Pin Assignment for the SINEC L2 Interface of the S5-95U
EWA 4NEB 812 6112-02
SINEC L2 interface
Communications
processor
Handling of
telegram
traffic
5
M 5V2 (data reference potential)
9
4
RTS (transmit request)
8
3
RXD/TXD (B) (data line B)
7
2
Not assigned
6
1
PE (ground)
Start-Up, Tests, and Diagnostics
5
9
4
8
3
7
2
6
1
3-3