17
saia-pcd.com
5
Switch cabinet
components
4
Consumer
data acquisition
3
Dedicated
room controllers
2
Operation
and monitoring
1
Automation
stations
Automation stations – the basics
Can third-party local I/Os be connected via S-Bus?
In the manual we have excluded these for the Saia PCD®
controllers. SBC S-Bus is a proprietary protocol that is es-
sentially designed for communication with engineering
and debugging tools, to connect the management level
or process control systems and for PCD to PCD commu-
nication. It is not suitable or approved for the connec-
tion of local I/Os from different manufacturers. I/Os from
third-party manufacturers should be integrated profes-
sionally and safely using one of the many manufacturer-
independent field bus systems.
Can the Saia PCD controllers connect direct to the
Internet?
When Saia PCD controllers are connected direct to the
Internet, they are also a potential target of cyber attacks.
Appropriate protective measures must always be taken
to guarantee secure operation.
PCD controllers include simple, integrated protection
features. However, secure operation on the Internet is
only ensured if external routers are used with a firewall
and encrypted VPN connections. For more information,
please refer to our support site:
/
security
How do I connect a third-party device to the PCD if
the protocol is not supported in the PCD firmware
and there is not a corresponding FBox library either?
One of the greatest strengths of the Saia PCD® is that, in
addition to the numerous “off the shelf” communication
protocols available, users themselves can implement any
protocol required in the user program. This is possible via
a serial interface and also via Ethernet.
You can find PG5 example programs on our support site
on this topic.
FAQs for the design of automation systems
What is the difference between centralised and
decentralised I/Os?
When remote I/Os are accessed, a communications
task always has to run. This task interrupts the process-
ing of the actual ICA task, thus extending the cycle
time (page 11). If cycle time is important and critical,
it is more efficient to use central I/Os.
Howmany central I/Os per Saia PCD®?
The I/O capacity of a Saia PCD® automation station
depends on the maximum number of pluggable
I/O modules, i.e. 64 modules for the Saia PCD2 and
Saia PCD3 series. Each module requires 16 bits. This
gives a maximum of 1024 binary signals overall. Each
Saia PCD® CPU in this system catalogue can read all
1024 binary signals in under 10 msec and make them
available to the user program logic. For calculation
purposes, assume a value of 0.01 msec per binary I/O
and 0.03 msec per analogue value.
In practice, the number of I/Os is limited by the cycle
time required for the user program (see explanation
page 11). If the Saia PG5® IL Editor is used to write a
resource-efficient user program in text form, the 64
I/O slots of the Saia PCD® automation station will be
fully usable. The cycle time will certainly be well below
100 msec.
If the graphic software engineering tool Saia PG5®
Fupla and prefabricated system templates (Saia PG5®
DDC Suite) are used to create the application software,
then only half the 64 possible I/O modules should be
equipped for a cycle time of <100 msec. Additional
communication and data processing tasks will further
increase cycle time.
In the case of fully graphic software engineering for
control-intensive applications combined with ad-
ditional tasks (e.g., BACnet®, gateway, management
functions), it is inadvisable to use more than 300 I/Os
per automation station.
