User Manual

2
Modbus Interface Specifications
Modbus Gateway
12
Building Technologies
A6V10316242_a_en
CPS Fire Safety
31.05.2019
2 Modbus Interface Specifications
The Modbus gateway enables Modbus master/client stations to access the
FS20/FS720/STT20 fire control units for acquiring the status information.
The gateway also allows for control commands to be transmitted from the Modbus
master/client stations to the fire system. A specific agreement with Siemens is
required for this type of functions.
This document deals with the application-level communication and illustrates the
register maps used for implementing it. For information about the physical
protocols involved and the related configuration procedures, please refer to the
NK8237 Installation, Configuration, and Commissioning Guide (document no.
A6V10316241).
2.1 Modbus Gateway
2.1.1 Modbus Connections
Up to four Modbus protocols can be handled, via serial and/or TCP/IP connection:
 Serial connection: two links as Modbus slave in RTU mode over an RS232 or
RS485 line.
 TCP/IP connection: Modbus server for four TCP/IP client connections.
Separate Ethernet ports can be used for BACnet/IP and Modbus TCP/IP for
maximum protection of the safety network.
Modbus hosts and system limits per each connected NK823x unit
Modbus hosts
Detectors and units per NK823x
1 Modbus host
 Max 10,000 detectors
 16 FS20/FS720 units
- OR -
12 FS20/FS720 units and 10 STT20 units in FCnet/SAFEDLINK topology
2 Modbus hosts
 Max 5,000 detectors
 8 FS20/FS720 units
- OR -
6 FS20/FS720 units and 5 STT20 units in FCnet/SAFEDLINK topology
3 Modbus hosts
 Max 3,500 detectors
 6 FS20/FS720 units
- OR -
5 FS20/FS720 units and 3 STT20 units in FCnet/SAFEDLINK topology
4 Modbus hosts
 Max 2,500 detectors
 4 FS20/FS720 units
- OR -
3 FS20/FS720 units and 2 STT20 units in FCnet/SAFEDLINK topology