Introduction

Flash memory is an essential component in modern electronics, providing non-volatile data storage in a variety of applications. The AB28F200BRB80, a 2-Mbit (256KB x 8 or 128KB x 16) Flash memory chip, offers flexibility in addressing and compactness suitable for DIY enthusiasts. In this project, we will design and build a Simple Data Storage and Retrieval System using the AB28F200BRB80, focusing on reading and writing data to flash memory via basic control hardware.

Project Overview

The goal is to create a hardware-based solution for storing and retrieving small datasets using the AB28F200BRB80 chip. This project does not involve programming; instead, it relies on hardware switches, control circuits, and LEDs for status indication.

This system could be a stepping stone for implementing data logging systems, configuration storage, or even educational purposes to learn how flash memory operates.

Key Features of the Project

1. Data Storage: Write a series of 8-bit data values into the flash memory.

2. Data Retrieval: Read and display stored values via LEDs.

3. Hardware Controls: Use switches to control the addressing and data input/output.

4. Indication System: Use LEDs to visualize data being stored and retrieved.

5. Expandable Design: Easily scalable to larger systems or interfaced with microcontrollers.

Components Needed

1. AB28F200BRB80 Flash Memory IC

1) Memory type: Flash

2) Size: 2 Mbit

3) Pin configuration: TSOP or DIP package (depending on availability)

2. 74HC244 Octal Buffer IC (or equivalent)

For address and data signal buffering.

3. 74LS138 3-to-8 Decoder

For address decoding to control memory operations.

4. 555 Timer IC

Generates control signals for timing.

5. Push-button Switches (x8)

For manual data entry (binary format).

6. LEDs (x8)

Display output data.

7. Resistors

Various values for pull-up/pull-down networks.

8. Capacitors

For filtering and decoupling.

9. Power Supply

+5V regulated supply for all components.

10. Miscellaneous:

Breadboard, jumper wires, sockets, and connectors.

Understanding the AB28F200BRB80 Flash Memory

Before diving into the circuit, it's essential to understand the memory's basic functionality:

1. Address Lines (A0 to A17): Select the specific memory location to read or write.

2. Data Lines (D0 to D15): Handle the data read from or written to the memory.

3. Control Lines:

1) CE# (Chip Enable): Activates the memory.

2) OE# (Output Enable): Enables the data output during a read operation.

3) WE# (Write Enable): Enables data writing.

4. Byte/Word Mode Select (BYTE#): Configures the chip for 8-bit or 16-bit operation.

Step-by-Step Design

1. Address and Data Selection

We will use the 74HC244 octal buffer IC to manage the address and data signals. This ensures a stable signal path and prevents any interference during operation.

1) Address Inputs: Use switches to set the address lines (A0 to A17).

2) Data Inputs/Outputs: Data to be written is manually input using push-button switches (D0 to D7). During read operations, the memory data will be displayed on LEDs.

2. Address Decoding

The 74LS138 3-to-8 decoder will simplify selecting memory blocks. The decoder's outputs will connect to the CE# line of the flash memory.

Address decoding will map specific memory regions to manual selection switches, allowing us to toggle between different memory blocks.

3. Read/Write Control

Using basic logic gates, you can generate the required signals for CE#, OE#, and WE#. For simplicity:

1) Push buttons will control the read/write operation.

2) A 555 timer will provide timing pulses for controlled operations.

4. Data Visualization

Connect 8 LEDs to the data lines (D0 to D7) through current-limiting resistors to display the memory's output during a read operation.

Circuit Design

Block Diagram:

1. Input Section:

Manual switches for address selection and data input.

2. Control Section:

Logic gates and timing circuits to manage CE#, OE#, and WE# signals.

3. Flash Memory Interface:

The AB28F200BRB80 is at the core, interfaced with buffers and decoders.

4. Output Section:

LEDs for data visualization.

Key Connections:

1. Address Lines (A0–A17): Connected to switches and buffered through the 74HC244.

2. Data Lines (D0–D7): Connected to both push-button switches (for write) and LEDs (for read).

3. Control Lines:

1) CE# controlled by a 74LS138 output.

2) OE# connected to a push button for manual enable.

3) WE# controlled via a combination of push buttons and a timer for pulse generation.

4. Power Supply: Ensure proper decoupling capacitors near the flash memory and buffer ICs.

System Operation

1. Writing Data

1. Set the desired memory address using the address switches.

2. Enter data using the push-button switches connected to the data lines.

3. Activate the write operation:

1) Press the WE# button to latch the data into memory at the selected address.

2) Ensure CE# is active, and OE# is inactive during this operation.

2. Reading Data

1. Set the memory address of the data you want to read.

2. Activate the read operation:

1) Press the OE# button to enable data output from the memory.

2) Ensure CE# is active, and WE# is inactive.

3. Observe the data output on the LEDs.

Project Assembly

1. Prototype the Circuit:

1) Use a breadboard for initial testing.

2) Connect components according to the circuit diagram, starting with the memory IC.

2. Test Individual Modules:

Verify address selection, data input, and output visualization independently.

3. Integrate the System:

Combine all modules and test for functionality.

4. Debugging Tips:

1) Check signal levels at control lines.

2) Ensure proper timing of CE#, OE#, and WE# signals.

3) Use a multimeter to check continuity and voltage levels.

Applications and Extensions

This project demonstrates the basics of using flash memory in DIY electronics. Once complete, you can extend the system by:

1. Adding a microcontroller to automate address selection and data transfer.

2. Integrating a keypad for user input.

3. Creating a simple data logger for environmental sensors or other devices.

Conclusion

This Simple Data Storage and Retrieval System using the AB28F200BRB80 is a practical and educational project for DIY electronics enthusiasts. It offers hands-on experience with flash memory, address decoding, and hardware control circuits. By following the steps outlined above, you can build a functional system and expand your understanding of non-volatile memory operations.