User Manual

Logical I/O blocks
Value objects for operation
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19.5 Value objects for operation
To simplify operation, use the value objects BVAL_OP, AVAL_OP and
MVAL_OP. The blocks are specifically intended for the operation of setpoints
via BACnet clients. They do not require a manual override from the operator
unit. Value objects look like all other blocks, and can be connected with other
blocks. The blocks do not include alarm generation or runtime totalization.
19.6 Addressing the I/O blocks
Logical I/O blocks allow the standardization of the inputs and outputs
irrespective of the hardware. The relationship between a given logical I/O and
its physical equivalent is established by assigning the address of the I/O
system concerned.
This independence has the advantage that the functions of the block, as
defined by the BACnet standard and the specific Desigo PX enhancements, do
not change. The number of different I/O systems or physical I/Os can be
expanded freely.
Another advantage is that the compound libraries are always identical. In the
engineering phase, they are adapted to the I/Os in the project by assigning the
appropriate addresses. The process values (0…10V, 0…25mA, signal contacts,
etc.) from the connected field devices are registered directly at the physical
inputs. The physical outputs deliver the process values (0…10V, switching
stages 0 / I /II / III, etc.) directly to the connected field devices.
The process values are transmitted in the form of raw data via the relevant
medium (e.g., PPS2); the conversion of the raw value takes place within the
block.
Rules:
● Values from the plant are measured and processed in Input blocks (Analog,
Binary or Multistate).
● Values to the plant are processed and transmitted by Output blocks
(Analog, Binary or Multistate).
I/O systems
To enable the process value of the logical I/O block to be allocated to the
appropriate physical I/O, the relevant address must be assigned. The address is
assigned as follows:
● Via automated assignment by the Point Configurator to the CFC
● Direct allocation to the I/O block in Xworks Plus (XWP)
T
R
I/O module
Physical
input
Program in XWP
Block
AI
Island bus
10664-24Z01en
R
Logical
input
Logical
output
I/O module
Physical
output
BO
Island bus
Hardware
independence
Identical compound
libraries