Introduction to MARIE Computer Architecture

Each instruction appears to be very simplistic; however, if you examine what actually happens at the component level, each instruction involves multiple operations.  For example, the Load instruction loads the contents of the given memory location into the AC register. But, if we observe what is happening at the component level, we see that multiple “mini-instructions ” are being executed.  First, the address from the instruction must be loaded into the MAR.  Then the data in memory at this location must be loaded into the MBR.  Then the MBR must be loaded into the AC.  These mini-instructions are called micro operations and specify the elementary operations that can be performed on data stored in registers.  The symbolic notation used to describe the behavior of micro operations is called register transfer notation (______) or register transfer language (RTL).  We use the notation M[X] to indicate the actual data stored at location X in memory, and ← to indicate a transfer of information.