The control store is similar to the ROM in
that the control store holds information that cannot be changed or erased.
The control store contains the set of
micro-instructions that are used
to execute all of the programs run on that computer. The control store is
referenced by the MPC, the micro-program counter, a device similar to a
register. The
MPC stores the location of the microinstruction that is
currently being executed. The MPC is regulated by the
MMUX, a device that determines if the MPC should be
incremented or if it should jump to an entirely new instruction. A jump
would only occur if certain conditions were met, usually dependent on the
ALU's output.