What makes PLC work? (which Processors)

Hello folks,

Ever wondered what makes this PLCs work? Which MicroProcessors/ MicroControllers goes inside? Are the Custombuilt?

What OS do they have? Who manufactures them? Sometimes I think that we PLC programmers area at the application end and the lasting impression we have is from the compiler we use for respective PLC. We decide the better one only from the couple of instruction differences.

May be the Embedded software/ VLSI,ASIC community laughs at our forums/ discussion as we would do if our dumb customers start a forum on the Systems we commissioned at their plant and starts discussing who is better? This thought moved me so much that I am even thinking of persuing an Embedded Systems Course. Your response on this will be appreciated.
(I know my collegues are laughing at me........ )


I have heard that Siemens uses Motorola Processsors for their PLCs and even AB does the same. Is it really so? I think this information is not easily accessible. I would like to have it if anybody have an idea about where to find it.

Thanks for reading all this and sorry if you think you wasted your time......... Yes, I didn't really mean the later part!!!!!!

Guest

Regard photo http://s7detali.narod.ru
inside old and new s7 315-2DP
in old 16 bit Infineon C166, in new - Siemens/Infineon (core C166)

That was coooooool.........

Wish I could understand russian, I guess it is.

I Think other folks are not interested. Nevermind.

May they live in interesting times.

It is not a waste of time to understand how things work.

lucifer said:

Hello folks,

Ever wondered what makes this PLCs work? Which MicroProcessors/ MicroControllers goes inside? Are the Custombuilt?

Click to expand...

I used to be interested in that sort of thing. See my other posts on this topic.

lucifer said:

What OS do they have? Who manufactures them? Sometimes I think that we PLC programmers area at the application end and the lasting impression we have is from the compiler we use for respective PLC. We decide the better one only from the couple of instruction differences.

Click to expand...

Yes, it is the software that is most important. I don't think they use an OS. They use an embedded kernel which is a stripped down OS

lucifer said:

May be the Embedded software/ VLSI,ASIC community laughs at our forums/ discussion as we would do if our dumb customers start a forum on the Systems we commissioned at their plant and starts discussing who is better? This thought moved me so much that I am even thinking of persuing an Embedded Systems Course. Your response on this will be appreciated.
(I know my collegues are laughing at me........ )

Click to expand...

This is a key point. No one is laughing if they are smart. See Phil's consumer report thread. Wouldn't you pay attention to what your customers are saying about your systems and your competitor's systems? A forum would provide cheap marketing feed back ( thanks Phil). A forum for 'dumb customers' about their systems would let you know what features you need to add to your systems and what features you need to change. I think that is valuable marketing data. I am here for the marketing info.

I like doing embedded software. I am also a BIG believer in FPGA ( field programmable gate arrays ), but I don't have time to learn the tools but I do get involved with the algorithms and features. Our FPGA designer can implement the equivalent of whole PLC programs where all the logic is run in PARALLEL within a microsecond. Terry would drool.

lucifer said:

I have heard that Simians uses Motorola Processors for their PLCs and even AB does the same. Is it really so? I think this information is not easily accessible. I would like to have it if anybody have an idea about where to find it.

Thanks for reading all this and sorry if you think you wasted your time......... Yes, I didn't really mean the later part!!!!!!

Click to expand...

Simatic TI uses Motorola, and so do the older Rockwell PLCs. The Control Logix is a FPGA or ASIC that I think has an ARM core with bus interface built in. This is a new trend. Our FPGA designer just got back from an embedded developers conference in Los Angeles. He was telling me the FPGAs are so big that one can put a CPU and the feedback logic into the FPGA for doing motion, and another CPU with a field bus interface all in one FPGA. When the FPGA chip becomes obsolete, the FPGA designer just buys the next generation of FPGA which will be bigger ( more gates, not physically ) and faster and recompiles his FPGA code and pours his old design into the new FPGA.

IT IS THE SOFTWARE THAT IS MOST IMPORTANT!!!

I read very recently that the AMD 2901 or 2903 (bit-slice processor) was used in A-B's PLC-3, among others.

Extra credit: Anybody care to speculate which eight instructions the 2901 ALU can perform? I have my own list made up.

p.s. Don't everybody rush in just to post the answers, give the guys just starting out a chance to think it over and post first.

Wow, the amount of knowledge on this forum is amazing. Thanks for the answers guys, will read up when i’m done comissioning!

swedeleaner said:

Wow, the amount of knowledge on this forum is amazing. Thanks for the answers guys, will read up when i’m done comissioning!

Click to expand...

It's probably improved in the 16 years since this was last discussed......

Not really following you Mr Tragic... Is the info provided obsolete? And if it is, please point it out. I do wanna learn more, but info that is obsolete are not of interest.

The GE (now Emerson) RX3i PLCs I use have a Linux OS.

You got me curious so I took apart my testing AB SLC 5/05 and it has:
MC68020EH16E-ND Microprocessor
MC68882EI16A-ND co-processor


All of which the chip suppliers say are obsolete.

swedeleaner said:

Not really following you Mr Tragic... Is the info provided obsolete? And if it is, please point it out. I do wanna learn more, but info that is obsolete are not of interest.

Click to expand...

The original info is 16 years old, I don't know if its obsolete as I don't care what OS the PLC is running or what processor it uses.

For a PLC you need something much more reliable than the processor of a PC, even if they are older CPUs, they must last for years running without crashes.

lfe said:

For a PLC you need something much more reliable than the processor of a PC, even if they are older CPUs, they must last for years running without crashes.

Click to expand...

I'd hazard that 99% of crashes are software based.

cardosocea said:

I'd hazard that 99% of crashes are software based.

Click to expand...

+1
It’s all microprocessors wether it’s a PLC or a PC..
Purpose built OS, and very limited hardware/Software compability is probably what differs.