In Fall 2023 and Spring 2025, I (Austin) introduce the LC-3 datapath piece-by-piece, adding components as needed, rather than all at once. (In Fall 2023, Pulkit Gupta helped figure out the initial approach for this. As of Spring 2025, Dan Forsyth and Mark Moss also take the same approach in the lecture slides on Canvas.)
My (Austin's) lectures are taught using printouts of
story-of-the-lc3-datapath.pdf. You can rebuild that PDF if you have
Inkscape and poppler-utils installed by running make.
The datapath drawings in this repository are taken from Patt & Patel 3rd
ed., specifically the diagrams on page 174 and page 704. We've made some
minor changes, though: the MDR no longer mysteriously has two inputs; the
confusing R.W label is drawn as a separate wire labeled MEM.RW; the INPUT
and OUTPUT boxes are removed since we won't cover I/O until later; and the
muxes for SR1 and DR are drawn explicitly instead of being magical.