Future Design MCTB 4.3, Руководство пользователя

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MCTB
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The most commonly overlooked source of problems is cabling. Not all cables are created equal. Electrical
noise generated by factory equipment or other electrical equipment in the area, could easily corrupt transmitted
data over the net
work and cause devices to “lock up” or shut down the VNC server, both of which then require
the MCTB to be shut down and restarted to clear the problem.
Select the right cable for the environment. Shielded twisted pair (STP) cable is naturally more noise immune
and is preferable to unshielded twisted pair or UTP in noisy situations. STP should have at least 40dB CMRR
and less than 0.1pF capacitance unbalance per foot. Ground STP cable, making sure the ground is connected
only at one end. CAT5 STP patch panels normally provide a grounding strip or bar.
Hubs and switches don’t
provide grounding, use cables.
It’s wise to be pessimistic about a cable’s ability to reject noise from 230 VAC and 460 VAC power lines and
electrically “noisy” equipment in the area. Capacitance imbalance in cables greater than 70pF per 100m can
introduce harmonic distortion resulting in bit errors. The cost of cable is quite small compared to total equipment
cost, so if you’re looking to save money, this is not a place to do it. Choose a well-designed cable to minimize
bit-error rate after installation, and that will give faster throughput with fewer glitches.
11.1.1.1 The MCTB and Network Security
When most people think of security, they think of anti-virus programs and continuous operating system updates
t
o insure their system is running with the “latest-and-greatest” software. For consumer devices, this is well and
good, but when it comes to industrial devices not so much. How many times has an update to the OS caused
an issue with an existing program that for now some reason is not working correctly or crashes inexplicably.
How about an anti-virus program updating its threat definitions and now sees an application as a potential threat
and blocking it from operating? To have this occur on a control device could be catastrophic to a process. So
how does the MCTB address these concerns while still providing threat protection?
The MCTB software validation uses a specific OS version and revision number as part of the validation
process. WinCE is not the same as Win7, 10, etc. and does not support automatic updates since the OS must
be installed in a specific portion of memory using a cable or SD with the device present. The OS layout is also
specific to the hardware on the device. FDC has never had an update to the OS unless the hardware changed
on our units which required a driver (mostly third party) for the new hardware. This also provides stability since
this is an industrial device that provides specific functionality without most of the “overhead” of the OS’s that full
PC’s run.
Most security issues arise from browsing or opening an email attachment that carries harmful code. The MCTB
does not support the addition of anti-virus software: however, the MCTB does not have a browser or an email
server to receive emails or attachments. The FTP, FileWeb and DataWeb interfaces are also client based only.
They transmit files and data to remote servers, but do not receive.
The MCTB writes data to a web page in memory that can be accessed by an external browser. This is a read
only web page (from the remote browser) that contains process values, set points, event and current program
data only. The internal web page data is written over with real time data every 30 seconds. The MCTB does
not read any data from its internal web page so any corruption of the web page would not affect MCTB
display/control operations. There are no passwords or sensitive data sent from the remote browser to the
“read only” web page.
A virus to attack Windows CE would be difficult, but not impossible. Every Windows CE device is different (by
manufacturer), so not an easy standard to write the virus against. The virus would need to be built for Windows
CE and the CPU that the MCTB runs, and the storage device doesn't have a standard name. There might be
industrial devices that run anti-virus on their CE devices; however, FDC is not aware of any. As the saying
goes, the best defense is a good offense. It is best to design a “smart network” to prevent intruders from gaining
access in the first place than to try and fend them off once they are already in the door.