Hello David;

I am afraid that the type of information you are looking for on the CPU architecture is well protected by Siemens and not divulged to the public easily.

The following represent the type of information you can find on the forum on the same subject; whatever details on the family of chips used in the S7-300 are mostly anecdotal:

https://support.industry.siemens.com/tf/WW/en/posts/what-is-the-architecture-of-s7-cpu-s/28738?page=0&pageSize=10

https://support.industry.siemens.com/cs/document/21064245/the-s7-architecture?dti=0&lc=en-WW

Now, all digital systems in use today are microcontroller-based, that is a microprocessor with memory chips and an address bus and a clock.

Gnerally most microcontrollers oin the market have a small kernel of basic controls, you have to program all the functionnalities you want to develop.

A PLC is a microcontroller system with dedicated operating system (some of the newer systems even use Windows, but they are the exception; Beckhoff for example needs a Real-time extension to Windows to run the scan adequately)., allowing the interface of digital, analog and functionnal I/O modules, that operates on a cyclic scan of all I/Os and programmed functions.

Programming is sytemized through a programming software that generally accesses basic functiuons (binary and logic instructions, analog procressing, communications over Fieldbuses, etc...).

At the difference of a PC, there are no input/output peripherals mounted to a PLC: no keyboard, mouse or video screen. Nothig from the user must interrupt the scan, so the PLC can operate as fast and reliably as possible, 24/7/365. To see, monitor or change the program you must connect a programming PC with the programming software to the PLC programming port.

Hope this helps,

Daniel Chartier