User Manual

Logical I/O blocks
Addressing the I/O blocks
19
266 | 351 CM110664en_07
PX compact PXC12.D
PXC12-E.D
PXC22.D
PXC22-E.D
PXC36.D
PXC36-E.D
Module Channel Module
UIO
Universal I/O
with Q250
4 1..4
U1..U4
4 1..4
U1..U4
4 1..4
U1..U6
R1K, U10, T1,
N1K, P1K, C,
D20, D20S,
Q250
Layout of PXC36.D housing with address ranges
See
Automation stations, compact model PXC..D (CM1N9215).
Multiple use of sensors
Multiple use of I/O signals
Multiple use by addressing the physical I/Os in two or more logical I/O blocks (as shown in the following
figure) is not allowed.
If you wire it as in the figure above, Xworks Plus (XWP) determines multiple use and generates an error
message.
For the multiple use of output blocks, the plant will malfunction, because there will then be two or more
sources acting on one switching command. The effective switching command (at the output) is the last one
received (determined by the rule "the last command takes precedence"). In other words, the order of
processing determines which source or origin will be linked to the output.
In CFC the same address can be allocated to two or more input or output blocks. This multiple address
allocation goes undetected when the program is compiled; the automation station also fails to recognize
the error (a reliability error is generated and an error message is transmitted only in the case of multiple
address allocation with two different signal types).
Solution 1
Many systems include a requirement for the multiple use of sensors. A typical example of this is an outdoor
air temperature sensor shared across systems. The following example illustrates the simplest form of the
multiple use of sensors:
In CFC the current value is transmitted for further use in the program by interconnecting the blocks. The
logical I/O block (Analog Input, {AI}) occurs in the program once only, and its hardware-specific parameters
only need to be set once.
HMI / TOOL
DO1
U1 U2 U3 U4
U5 U6 U7 U8
U9 U10 U11 U12
U13 U14 U15 U16
U17
U18
U19
U20
U21
U22
U23
U24
T
AI
Island bus
R
I/O module
Program in XWP
Block
1
0
6
6
4
-
2
4
z
0
2
e
n
AI
Island bus