OVERVIEW

All I/O modules are connected to the high-speed Bus Interface Module (BIM) via a proprietary bus system called “Railbus”.

Up to 32 modules can be connected to one BIM. The module backplane provides the transmission medium for the Railbus.

At the same time, the modules can be connected to the bus by plugging them into the base plate. The connectors on the base plate also provide the power www.cniacs.com supply for the modules and, if necessary, for the field wiring.

Addressing of I/O modules

Modules are addressed by the bus interface module according to their location or slot and by combinations of 32 modules rather than individual module types.

Modules can therefore be removed and replaced by another module of the same type without “informing” the Bus Interface Module.

During the configuration process, the Bus Interface Module is informed of the location characteristics of each required module, regardless of whether the module is present at the time.

Therefore, if a module is replaced, the attributes of that “slot” remain with the bus interface module.

Critical modes

Output fail-safe mode

The output module can enter a fail-safe state. The module will enter this state if either of the following two reasons occur.

(1) The BIM forces the module into a fail-safe state by issuing a special command.

(2) The module has a configurable “timeout” parameter. This allows you to specify a maximum amount of time that communication with the BIM will cease.

Once this time is exceeded, the module will go to a fail-safe state. Different types of modules respond to fail-safe commands in their own ways, which are described separately in the following sections.

Input Fault Value

If a fault occurs in the input module, the BIM forces the reported value into a predefined state – Low, High or Hold Last.

This ensures that the host computer adopts a state consistent with the safe operation of the unit.

Power-up/Initialization Status

Knowing the state of each output when the node is powered up is critical to ensuring the safety of the device.

While the BIM is initializing, the I/O modules remain powered up (see next page for details). After the BIM is initialized, and before communicating with the host computer, the outputs are set to the predefined “outputs”.

The outputs are set to a predefined “initialized” state. This “safe state” can be defined by the user.