8. Bit Patterns, Instructions, and Registers
Feel free to use your laptop
You are strongly encourage to work with others
When you get stuck, ask those sitting around you for help
Get used to working together in the labs
Peer teaching and peer learning has been empirically shown to be very effective
For these questions, feel free to use a single Digital workspace for all the circuits. However, label each circuit with labelled rectangles. These are components that can be found under Components -> Misc. -> Decoration -> Rectangle.
Where possible, each question should have complete tests. The test component can be found under Components -> Misc. -> Test case. Once a test component is placed on the workspace, right click on the component to edit the test data.
Questions may have restrictions on the logic gates that may be used. When restrictions are stated, they only apply to the gates; inputs, outputs, wires, etc. may be still be used.
8.1. Prepare
If not already completed, finish the design from the previous lab
8.2. Registers
Modify the design such that the values do not come from 8 bit inputs, but from registers
This will be similar to assignment 3
The updated design should include eight 8 bit registers
Two sets of 3 bit values will be used to specify the two registers the values should be retrieved from
The design will have 1 output
This new design will have a total of 10 inputs
One 1 bit input specifying ALU or comparator
One set of 3 bit inputs specifying an operator
Two sets of 3 bit inputs specifying the sources of the two inputs to the ALU/comparator
Modify the design such that the result is not only output, but saved to a specified register
This design will have 1 output
This design will have 13 inputs
The same 10 inputs discussed above
An additional 3 inputs specifying which register the output should be saved to
8.3. New Operation
Currently there is no way to actually load data into the system.
Add a new mode/instruction such that data can be loaded into a specific register
Currently 1 bit is used to specify ALU or comparator operations
These can be thought of as modes
Add an additional bit to allow for selecting between up to 4 modes
2 mode bits
3 bits that served as selecting a specific operation
Two sets of 3 bits for specifying 2 source registers
3 bits for a destination register
Update the system such that one of these 4 modes allows for loading data directly to a register
The 3 destination register bits specify where the data is to be stored
8 bits of the 9 available for the operator and 3 source registers specify the 8 bit data
For example, consider the below bit patterns and their meanings
00 110 101 010 111—addon registers 5 and 2 and store in 701 110 101 010 111—>=on registers 5 and 2 and store in 710 1 10101010 111— Store0b10101010(170) in register 7
Add a new forth mode such that data can be copy between registers
Here, only one set of 3 bits specifying the source register is required
11 110 101 010 111— Copy contests of register 2 to register 7