Customising The Modbus Interface; General Gateway Parameters; General Parameters Configuration Procedures - Siemens NK8237 MP4.40 Installation, Function & Configuration, Commissioning

7.7

Customising the Modbus interface

7.7.1

General gateway parameters

7.7.2

General parameters configuration procedures

Building Technologies
Fire Safety & Security Products
In the Modbus Master node, a number of configuration settings can be custom-
ised related to general NK8237 gateway parameters as well as to the address of
Modbus devices and data tables.
The NK8237 handles a number of data tables to implement the Modbus commu-
nication at application level. A detailed documentation of these tables is provided
in the NK8237 Interface Specifications guide (document no. A6V10316242).
The general parameters include:
 Command level
This parameter defines the command access level allowed for the Modbus mas-
ter station. The option list includes:
 No command: the Modbus master station cannot send any command to the
fire system.
 Ack only: the Modbus master station can only send the Acknowledgement
command to the fire system.
 Ack, Reset: the Modbus master station can only send the Acknowledge-
ment and Reset commands to the fire system.
 Ack, Reset, Basic command: the Modbus master station can send the
complete set of defined commands to the fire system.
 Watchdog timeout
This parameter defines a maximum delay (in seconds) for the Modbus master
station to poll the Modbus virtual devices (NK8237 and FS20/FS720 units). If
the timeout of the polling of one of the Modbus virtual devices expires, the
NK8237 generates a fault condition that is reflected in the Modbus register area,
in the diagnostic LED (blinking 6 times) and, if the relay output is configured
(see p.46), also as a relay output activation.
 Time synchronization
The time synchronization is important for setting the appropriate time stamp on
the exchanged data messages.
The NK8237 can handle the time synchronization in two ways. It can:
1. Receive date & time synchronization from the Modbus master station.
OR
2. Acquire date & time from the FS20 system every day at a given time.
Configuring the command level
1. Select the Modbus Master node.
2. Select the Host tab.
3. In the Command Level field, choose the required access level.
Configuring the watchdog timeout
1. Select the Modbus Master node.
2. Select the Host tab.
048_DMS_NK8237_ICC_MP4.40_A6V10316241_a_en.doc
Configuration
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06.2011