Chip overview
-------------

The picture shown below allows you to see the chip
you are about to design. As you can see, the circuit is
pretty small and self-explanatory. It mostly
consists in a 4 bit adder, a 4 bit register, and 2x1
4 bit multiplexer. Inputs are located on the left side of
the picture, and outputs are located on the right side.
Pay special attention to terminals sel and ck, as
they basically control the behavior of the circuit.

Block on the left is a 4 bit 2-to-1 multiplexer.
Upper right block is a 4 bit adder.
Lower right block is a 4 bit edge triggered flip-flop.


                                             ----------
b0 >-----------------------------------------|        |
                                             |        |
b1 >-----------------------------------------|        |
                                             |        |
b2 >-----------------------------------------|        |
                                             |        |--+---------------> s0
b3 >-----------------------------------------|        |  |
                                             |        |--|--+------------> s1
                                             | 4 bit  |  |  |
sel >------------------                      | adder  |--|--|--+---------> s2
                      |                      |        |  |  |  |
                  ----------                 |        |--|--|--|--+------> s3
a0 >--------------|\       |   --------------|        |  |  |  |  |
                  | \      |   |             |        |  |  |  |  |
a1 >--------------|  \     |   |  -----------|        |  |  |  |  |
                  |   \    |   |  |          |        |  |  |  |  |
a2 >--------------|    \   |   |  |  --------|        |  |  |  |  |
                  |     \  |----  |  |       |        |  |  |  |  |
a3 >--------------|      \ |      |  |  -----|        |  |  |  |  |
                  |       \|-------  |  |    ----------  |  |  |  |
                  |       /|         |  |                |  |  |  |
       -----------|      / |----------  |                |  |  |  |
       |          |     /  |            |                |  |  |  |
       |  --------|    /   |-------------                |  |  |  |
       |  |       |   /    |                             |  |  |  |
       |  |  -----|  /     |                             |  |  |  |
       |  |  |    | /      |                             |  |  |  |
       |  |  |  --|/       |                             |  |  |  |
       |  |  |  | ----------                             |  |  |  |
       |  |  |  |                            ---------   |  |  |  |
       |  |  |  -----------------------------|       |---+--+--+---
       |  |  |                               |       |   |  |  |
       |  |  --------------------------------| 4 bit |---+--+---
       |  |                                  | flip- |   |  |
       |  -----------------------------------| flop  |---+---
       |                                     |       |   |
       --------------------------------------|   /\  |----
                                             ---/--\--
                                                  |   
                                                  ^
                                                  ck
Press <return> to continue.
