Our ISA supports a very simple circuit design, relying on a single implicit $res register that acts like an accumulator to do most of the heavy lifting. All operations that are implemented: add, branch, load, store, to name a few will use $res in some way shape or form.

**res: ** Set $res to a 16 bit signed constant.

**Shift: ** Shifts $res by the amount defined by the decimal value of the operand.

**Add: ** Takes one operand register and adds its value into whatever is in $res.

**Load: ** Loads into a register the value at the address specified by $res.

**Store: ** Store into memory location specified by $res whatever value is in the operand register.

**Jump: ** Moves the PC forward or backward the amount specified in the operand register.

**Branch: ** Handles all branching, generally can check for less than, greater than, or equal to. Uses two special 'comparison' registers to do this.

** LSBTOG ** This will change the least significant bit of the of the register specified in the instruction depending on what is in $res using a combination of NOT and AND operations.

** Cpin ** This copies the value of the specified register into $res.

** Cpout ** This copies the values of $res into the specified register.

** Comp ** This compares whatever is in the specified register with whatever is in $res, and sets $res to 0 if $res is less than the speficied register, otherwise #res is set to 1.

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We expect ____ ALU operations?

• Add
• Subtract (or signed add)
• OR
• AND
• NOT
• ...