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ATS Designers Guide 37

default, after system memory restart, only the RAS number 1 is pooled. All RAS device

activity is saved in the system according to their number. The RAS station number also

defines the door number for central station based access control.

3.1.3 Bus topology

In accordance with the RS485 interface specification, the basic layout for the system bus

is a cascade connection of 32 devices. 16 RAS devices and 15 DGP devices can be

connected to the Advisor MASTER system data bus, which, along with the control panel,

gives 32 sending/receiving devices connected to the RS485 interface.

The bus configuration limits are imposed by the signal propagation in complex networks.

The signal “echoes” – a consequence of the signal bouncing in long network branches

due to different branches delay time – can cause multiple responses from one module,

which would be interpreted by the control panel as system sabotage. According to its

design, a system of class 3 and 4 should recognize and react to subsystem shutdown

attempts by switching devices. The echo effect can be mitigated through the use of

ATS174x bus expansion modules. The maximum bus length limits come from timing

dependencies of the device querying procedure. Any pooling errors or problems can be

read from the system menu, or through the diagnostic module of the TITAN software.

Each device connected to the ATS control panel has an inbuilt communication error

counter (max 255). That information can be used to test the bus configuration after

system installation.

3.1.3.1 Standard configurations

Because using only the cascade connection of system devices could be problematic,

some modifications of the cascade connection, as well as developing more complex

networks is permissible using the system bus accessories – the ATS174x devices.

. . . .

1500m

Drawing 3-4 Cascade connection

Standard data bus connections are the cascade connection and cascade connection with

branches up to 1500m. The control panel can be located in an arbitrary location in the

chain creating two branches. It has to be kept in mind that the total length of the bus

cannot exceed 1500m.

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Aritech ATS4000 Wartungshandbuch Seite 37