Yet again another very poorly written question, so we have PLC that controls a motor, but a PC, how does this connect.
Firstly if a motor is controlled by a PLC then the Pc must be some sort of interface i.e. a Scada or acting as an HMI, there is no clarity in this question.
The PLC controls the motor, the PC (assuming what is meant that the operator interface is from the PC) only reads the status or sends commands to the PLC to control the motor.
Again what is to say that the connection is 232 or modem (which is ambiguous in it'self as the modem will probably be 232) then there are other types of communication i.e. Ethernet, 485/422 etc.
I'm shaking my head here, this is the sort of question that might have been relevant many years ago. up & coming students are definitely going to struggle with their careers.
When I decided I would like to become a TV engineer (liked the idea of a company car & freedom of the road)in the 70's, I attended a course in advanced colour TV theory, that particular year the exam board decided to bring their exam papers in line with some of the newer technologies, actually there was only a couple of questions that were included, one was a new way of generating the colour burst signal, this is a a burst of waves every scan line at 4.433619mz, each alternate line was 90 deg out of phase, originally the phase difference was generated by using a delay line component, this question showed a way of using digital means, the crystal used for the colour burt was double i.e. 8.86 mhz, the signal was then put though a flip/flop digital ic so the result was 4.433619 mhz with alternate phases. at that time there were no actual TV models on the market, it was at least a year before these came out. I was the only one in the class who got that question right, the reason was that the circuit was a drawing of the logic & the question was what is this used for (so for the uninitiated this would mean absolutely nothing) however, I had done a digital electronics course so by using my knowlege I could work out what the waveform was from the logic, realising that 8.86 was double the colour burst frequency & resulting waveform was 90 Deg out of phase each scan line.
Right back to the post, it seems that there are a number of issues, many tutors or exam bodies are not any better at the command of the relevant language which is expected, their knowledge is far behind current tech.
My rant for the day......
