Okay. This is just to make sure I've got the first steps down pat.
The machine operates like this, right? The program counter starts off
at the first location in memory after the program is loaded into it.
It views the first thing there and adjusts the Program Counter
depending on what it finds there--a JMP command makes it go up by
three (the command is one byte in memory location, the location is
two), a BRK makes it go up by one. After it adjusts the Program
Counter, it carries out the command that it found at the memory
location. If the command is a JMP, it takes the bytes after the
command and puts it in the Program Counter. If it is a JSR, it takes
the number in the Program Counter, copies it to the Stack Pointer, and
places the bytes after the JSR command into the program counter.
Otherwise, it follows whatever the command is. In the event of a JSR,
it carries out the instructions from the point listed until it hits
the RTS. At RTS, it takes the top number from the Stack Pointer and
copies it to the Program Counter. The unit then moves everything in
the Stack Pointer up one (in the event of nested subroutines) and
continues on.
Have I got it? Do I get a gold star?
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