I/O blocks are used to register and transmit raw data to and from the plant, and to convert, process and integrate it into the program.

The following options are supported:

  • Raw data from or to the input or output modules.
  • Raw data from or to the PPS2 interface (room units) (not for the modular series PXC…D)
  • Data referenced via the Technical Designation (TD) and accessed either in the same automation station (without a connection), or peer-to-peer via BACnet services.
  • Data made available via a Discipline I/O of a room automation station or third-party device.

The term I/O blocks refers collectively to the individual input blocks and output blocks.

  • Input blocks are used to enable an input signal (e.g., a measured value) in the program to be handled as a process value.
  • Output blocks are used to enable a process value to be transmitted as an output signal (e.g., a positioning command).

Value blocks act as a link between program pins, and are used to temporarily store a process value, and if necessary, to display it on a client operator station. A special version of the value block, the Value block for operation provides a simplified means of operation from an operator client (without the facility to override values manually).

Counter Input blocks (CI blocks) are used to enable a counter value (e.g., from a gas or electricity meter) to be processed in the application as a real-number process value. In this process, the counter value (pulse) is converted in the block into the associated physical variable.

Integration I/Os (Discipline I/O blocks) are used, e.g., to integrate room automation or third-party devices

Input blocks

Output blocks

Value blocks

Value blocks for operation

Analog Input (AI, AI RED)

Analog Output (AO, AO RED)

Analog Input (AVAL)

Analog Input (AVAL_OP)

Binary Input (BI, BI RED)

Binary Output (BO, BO RED)

Binary (BVAL)

Binary (BVAL_OP)

Multistate Input (MI, MI RED)

Multistate Output (MO, MO RED)

Multistate (MVAL)

Multistate (MVAL_OP)

Counter Input (CI)




Accumulator (CI ACC)




Discipline I/O




Program view and system view

I/O blocks are displayed in two different views:

  • The program view shows an I/O block with the pins and attributes required for configuration purposes and to create the program. This is the display format used in Xworks Plus (XWP).
  • The system view shows the I/O blocks as standard BACnet objects. These BACnet objects and the associated properties are then available to clients from where they can be operated and monitored.

BACnet functions

All the blocks listed above are implemented in accordance with the BACnet standard. Therefore additional functions are available, such as alarm management. These blocks incorporate a mechanism which acts as an alarm source for blocks available as standard BACnet objects in the BACnet network. By use of various BACnet services, a given event is displayed as an alarm event on the relevant clients from where the alarm can be processed, that is, viewed, acknowledged and/or reset.

In XWP these functions can be tracked via the relevant values at the block pins in online test mode.