﻿ Digital Circuits and Systems - Circuits i Sistemes Digitals (CSD) - EETAC - UPC

 [7/10] Laboratory #4 [P3] Training on plan C2 structural hierarchical design [P3]  Arithmetic circuits: Adder_1bit, Adder_4bit, Adder_8bit

Plan C2 in the context of our VHDL design flow of combinational circuits. Let's describe hierarchical designs in VHDL using components and signals. Once you've learned how to do it, you can solve any large project in the same way.

Before attempting the Add_4bit or the Adder_8bit, study the following examples based on the plan C2:

Proposed top-down architecture <----> VHDL files

- Try again the MUX_8 but now using smaller components of the same kind MUX_8, plan C2. This problem can also be considered as a MUX2 and MUX 4 expanding.

- Let's solve for instance the Project A in P3: An Adder_1bit based on the method of multiplexers (MoM) and using a MUX2 and a MUX4.

- Let's solve for instance the Project B in P3: An Adder_1bit based on the method of decoders (MoD)

- Let's solve the Project C in P3: the (4-bit ripple-carry adder).

- Let's solve the Project  E in P3: The design of the

This is the due date for the PLA#1.1.

Questionnaire Q#1.1 on P1 - P2

Topics to be covered:

• Binary numbers, symbols, range and how to perform additions.

• Conversion from binary to decimal, decimal to binary, hexadecimal numbers.

• How to use the simple calculator in programming mode to works with bin/hex/oct/dec numbers.

Other basic operations in radix-2: comparison, multiplication, bit-shifting.

Study the 1-bit comparator complete tutorial example Comp_1bit, in this case a plan A (flat design based on an SoP structural architecture).

Example of an 8-bit multiplier.

 [10/10] Guided activities #4 [P4] Two's complement (2C) aritmetics for integer numbers

How to represent positive/negative numbers (integers): two's complement (2C) convention and range of values for a given number of N bits.

Operations with integers, overflow flag (OV): which is the algorithm to detect an overflow situation?

Play with the 8-bit adder/subtractor available in Proteus.  Addition: result R = A + B.  Subtraction: result R = A - B = A + (-B) = A + 2C(B) . The idea of a XOR gate of 2 inputs as a programmable (CNTL) inverter/buffer to be used as a 2C generator module.

There are other ways to implement substractors, like using a specific block Subtractor_1bit (see problem 3.10 in the CSD collection).

It is time for printing and reading the preparatory laboratory assignment PLA#1.2 for the next Lab #6