BLG242E -Experiment 6 Data Bus Implementation and Memory Design Solved

In this experiment, data buses and basic memory are going to be implemented by using three-state buffers.

You can use any operator/code block in this experiment. Using multiplexer structure is forbidden. You must simulate the all parts and modules.

1     Basic Principles
Buses are frequently used in digital systems in order to reduce the cost of the physical connections. For example, a digital system which consists of N distinct units requires N ·(N −1)/2 physical connections to create a fully connected network. Since providing distinct physical lines (wires) for each connection is an expensive approach, sub-set of digital elements communicates through the shared bus in time shared manner. A bus can be implemented as a wired OR circuit by using ICs with open collector outputs or it can be implemented by using 3-state buffers. Abstract design of the wired OR bus is given in the figure below.

 

Buses can also be implemented by using 3-state buffers. There is no need for a resistor in this design. Output a non-active 3-state buffer will be in high-impedance. There has to be only one active 3-state buffer which runs the bus as an output. An example implementation of a bus by using 3-state buffers is given below.

 

2     Part 1
In this part of the experiment, you should implement an 8-bit bus by using 3-state buffers. The circuit diagram is given in Figure 1.

Hint: You must use the three-state buffer as a module. Thus, you must design a three-state buffer module before implementing the circuit.

 

Figure 1: 8-bit data bus with 2 drivers with 3-state buffers

3     Part 2
 

Figure 2: 8-bit data bus with 2 drivers and 2 readers

In this part of the experiment, you should implement the circuit given in Figure 2. This circuit contains a bus with two distinct outputs and inputs.

4     Part 3
In this part, you should implement an 8-bit memory line module. This module should take 8-bit data as input and give 8-bit data as output. Also, the module should take reset, line select, read enable, write enable, and clock inputs for required operations. Required operations are given below.

•   At the rising edge of the clock signal, the module should store the data value which is given as input when the write enable and line select inputs are high.

•   The module should clear the stored data at the falling edge of the reset signal.

•   If read enable and line select inputs are high, the output of the module should be the stored data. Otherwise, the output should be high impedance.

5     Part 4
In this part, you should implement an 8 byte memory module using 8-bit memory line module. 8 byte memory module should take 8-bit data as input and give 8-bit data as output. Also, the module should take 3-bit address, chip select, reset, read enable, write enable, and clock inputs for required operations. Required operations are given below.

•   Nth memory line should be selected when the chip select input high. Here, N is address number.

•   At the rising edge of the clock signal, the selected memory line should store the data, which is given as input, if the write enable input is high.

•   The module should clear all stored data in the memory lines at the falling edge of the reset signal.

•   The output of the module should be the data of the selected memory line, if read enable input is high.

Hint: The output of the memory is a bus. Therefore, you do not need to use multiplexer in this experiment.

6     Part 5
In this part, you should implement a 32 byte memory module using 8 byte memory module. 32 byte memory module should take 8-bit data as input and give 8-bit data as output. Also, this module should take 5-bit address, reset, read enable, write enable, and clock inputs. 2 bits of the address input should be used for chip selection and rest of 3 bits should be used for selecting line. For instance, if the address input is 00111, zeroth chip (8-byte memory) and its 7th line (0-indexed) should be selected. Your module should be able to perform the operations below.

•   At the rising edge of the clock signal, the selected memory line should store the data value, which is given as input, if the write enable is high.

•   The module should clear the all stored data in the memory modules at the falling edge of the reset signal.

•   If read enable is high, the output of the module should be the stored data of the selected memory line.

Example Memory Simulation

•   Reset all lines

•   Write 25 to Address 30

•   Write 15 to Address 20

•   Read Address 12

•   Write 18 to Address 10

•   Read Address 15

•   Read Address 30

•   Read Address 10

7     Part 6
In this part, you should implement a 128 byte memory module using 32 byte memory module. 128 byte memory module should take 32-bit data as input and give 32-bit data as output. Also, this module should take address, reset, read enable, write enable and clock inputs. Your module should be able to perform the operations below. • At the rising edge of the clock signal, the selected memory line should store the data value, which is given as input, if the write enable is high.

• The module should clear the all stored data in the memory modules at the falling edge of the reset signal. • If read enable is high, the output of the module should be the stored data of the selected memory line.

Hint: 32 byte memory modules have 8-bit inputs and 8-bit outputs. You can use concatenate operation to implement 128 byte memory.

8     Report