updating PC wikki page

[vead]

hello
I need help to understand following diagram

what is M ? and how does PC receive input from output of ALU
output of ALU connected to input of PC
suppose PC is 16 bit and ALU is 8 bit

actually I am reading following page **broken link removed**

 

[betwixt]

Your link is wrong, but I found the page by searching. It explains what M is in the line below the diagram. It is the amount added to the program counter to advance it to the next instruction. It would not normally be the same ALU that the main processor core used for calculations. Normally it would be a loadable counter, it would increment as each sequential instruction was fetched and be loaded with a computed or absolute value if a branch or jump instruction was encountered.

In the case of 8-bit values being loaded to a larger PC, as is the case in PIC10,12 and 16 families, the remaining bits have to be copied from a bank or page register which is under user software control.

Brian.

 

[vead]

I have seen in many diagram some multiplexer connected between pc and ALU
. using multiplexer we can make some bit of counter low and some bit of counter High

I want to modify the diagram that I have posted in my first post to make loadable counter. assume I have connected multiplexer between the PC and ALU. how does PC know that instruction has been executed?. I will add another multiplexer later but I want to know why we are using multiplexer ?