User Manual

Logical I/O blocks
General functions
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19 Logical I/O blocks
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.
19.1 General functions
Blocks: AO, BO, MO, AVAL, BVAL, MVAL
This section describes the general functional scope shared by many of the I/O blocks. Each subsection
includes a list of the blocks to which that subsection applies. Any block-specific details which are not
shared by other blocks are described together with the block concerned.