Assignment

You and your partner will design, layout, and simulate a 4-bit calculator that performs the following functions:

1)  Addition of two 4-bit positive numbers

2)  Subtraction of two 4-bit positive numbers

3)  Multiplication of a 4-bit positive number by 2, 4, and 8

4)  Division of a 4-bit positive number by 2, 4, and 8

This design follows the structure of a finite state machine  --  the output of each computation will be used as an input to the next step. The clock is provided externally. The clock signal is a series of voltage pulses, swinging from GND = 0 V to VDD  = 1.2 V with a 50% duty cycle and 50 ps rise and fall times. The load capacitance connected to the outputs of the calculator is to be 50 fF.

Milestones

Due April 2:        Draw a complete block diagram that performs these tasks. (10 points)

Due April 9:        Learn to use hierarchical design in schematics and layout.  Learn to create a series of signals in HSpice. Draw a floorplan of your calculator. The floorplan includes the estimated geometric positioning of the layouts of different elements that considers continuous power rails ( VDD  and GND) across different cells and cascading. Submit the floorplan. (10 points)

Due April 16:      Design   and   simulate  your  transistor-level  calculator  schematic  in Cadence. (20 points)

Due April 30:      Finish  the  layout  of  your  design.  Show  that  a  large  portion  of  your schematic passes DRC/LVS. (10 points)

Due May 7:         Complete project with simulation of extracted layout. Prepare for a 5- minute class presentation demonstrating functionality, showing metrics, and explaining design choices. (30 points for completion, 20 point design competition)

Grading

You and your partner will receive the same grade. The final assignment will partially be graded comparatively, with the highest grade going to the group with the lowest area- energy-delay product, AEDP, defined as the area of the minimum bounding rectangle that encloses the full layout multiplied by the minimum possible clock period and the energy consumed to perform a set of testbench operations to be declared on April 30. You must declare what the clock frequency should be for the testing to verify functionality. Each operation is triggered by a positive edge of the clock and finished within one clock cycle. No late assignments will be accepted for any milestone.

Appendix

Instruction Set Architecture

INST [1:0] = 00: Addition; DATAOUT  [3:0] (n) = DATAOUT  [3:0] (n-1) + DATAIN  [3:0] (n)*

INST [1:0] = 01: Subtraction; DATAOUT  [3:0] (n) = DATAOUT  [3:0] (n-1) – DATAIN  [3:0] (n)*

INST [1:0] = 10: Multiplication; DATAIN  [2:0] (n) = 100, 010, 001 means multiplication by 8, 4, 2 on DATAOUT  [3:0] (n-1)*,#

INST [1:0] = 11: Division; DATAIN  [2:0] (n) = 100, 010, 001 means division by 8, 4, 2 on DATAOUT [3:0] (n-1)*,#

*Neglect the overflow bits

# Multiplication/Division by 000, 011, 101, 110, and 111 is not required

Sample Set of Operations

Reset:                   DATAOUT  = 0000 [Done with the reset input]

Operation 1           INST[1:0] = 00, DATAIN  = 0101                                  DATAOUT  = 0101

Operation 2           INST[1:0] = 01, DATAIN  = 0011                                  DATAOUT  = 0010

Operation 3           INST[1:0] = 00, DATAIN  = 0001                                  DATAOUT  = 0011

Operation 4           INST[1:0] = 10, DATAIN  = 0111                                   DATAOUT  = 0011

Operation 5           INST[1:0] = 10, DATAIN = 1011                                   DATAOUT  = 0011

Operation 6           INST[1:0] = 11, DATAIN  = 0011                                   DATAOUT  = 0011

Operation 7           INST[1:0] = 10, DATAIN  = 0010                                  DATAOUT  = 1100

Operation 8           INST[1:0] = 11, DATAIN  = 0001                                  DATAOUT  = 0110