Introduction to digital ICs 2716

Definition

The 2716 is a UV-erasable programmable read-only memory (UV EPROM) integrated circuit that stores 2048 words of 8 bits each. This means it can hold 2 kilobytes of data in binary form. It is programmed electrically, read electrically, and erased by exposure to ultraviolet light through a quartz window on the package.

In simple terms, the 2716 is a memory chip that allows a digital system to store permanent data such as firmware, lookup tables, or machine code, and later erase and reuse the chip when needed.

Main Content

1. First Concept: Structure and Memory Organization of 2716

The 2716 is organized as 2K × 8, meaning it contains 2048 memory locations, and each location stores 8 bits or 1 byte.
It requires 11 address lines because $2^{11} = 2048$ , so the address inputs can select any one of the 2048 bytes stored inside the chip.

The internal structure of the 2716 can be understood as a matrix of memory cells arranged so that each address points to one byte of data. When an address is placed on the address pins, the chip selects the corresponding memory location and outputs the stored 8-bit word on the data pins.

A simplified memory organization view:

Address Inputs (A0 to A10)
           |
           v
+--------------------------------+
|         2716 EPROM             |
|                                |
|  2048 locations × 8 bits       |
|  Location 0   -> 8-bit data    |
|  Location 1   -> 8-bit data    |
|  ...                           |
|  Location 2047 -> 8-bit data   |
+--------------------------------+
           |
           v
Data Outputs (D0 to D7)

This organization is extremely useful in digital systems because:

It provides direct storage of byte-sized information.
It matches the data width of many 8-bit processors.
It simplifies program storage and retrieval.

Typical use cases include storing:

Boot code
Fixed control programs
Character tables
Microcontroller-like firmware in older systems

2. Second Concept: Pin Configuration and Control Signals

The 2716 uses specific pins for address inputs, data outputs, power supply, programming, and control functions.
Important control pins typically include Chip Enable (CE), Output Enable (OE), and Program Voltage/Programming input, depending on the exact manufacturer version.

A standard understanding of the pin groups is essential:

Address pins

select the memory location.

Data pins

provide the 8-bit output.

Control pins

determine whether the chip is active, read-enabled, or being programmed.

Power pins

provide the operating voltage.

The role of these pins can be understood as follows:

Address pins (A0–A10)

Choose the memory cell or byte.

Data pins (D0–D7)

Send the stored data to the external system.

CE / Chip Enable

Activates the chip when low or high, depending on design.

OE / Output Enable

Enables the data output buffers.

VCC and GND

Provide operating power.

Programming-related pin(s)

Used during data writing into the EPROM.

A common operational interpretation is:

If the chip is not enabled, the outputs remain inactive.
If the chip is enabled and output is allowed, the stored data appears on the data bus.
During programming, a higher voltage is applied to force charge into the floating-gate transistors.

This pin-level understanding is important because digital ICs do not work simply by “having power”; they require correct control logic so that only the intended device drives the data bus.

3. Third Concept: Programming, Erasing, and Reading Operation

The 2716 stores information by using floating-gate transistor technology, which traps electrical charge.
It is programmed electrically, read electrically, and erased using ultraviolet light.

Programming

During programming:

A selected memory cell receives a high voltage pulse.
The charge becomes trapped in the floating gate.
The trapped charge changes the transistor’s threshold behavior.
This creates a stored binary value, usually represented as 0 or 1 depending on the architecture.

Reading

During reading:

The address lines select one byte.
CE and OE are activated.
The outputs drive the data bus with the stored 8-bit value.
No destruction of data occurs during reading.

Erasing

During erasing:

The EPROM package is exposed to UV light through its quartz window.
The ultraviolet energy removes trapped charge from the floating gate.
The entire memory becomes reset, usually to all 1s in many EPROM types.
After erasure, the chip can be programmed again.

This makes the 2716 reusable, unlike PROMs that are one-time programmable.

4. Fourth Concept: Characteristics and Technical Significance

The 2716 is a non-volatile memory, so it preserves data when power is off.
It is a parallel memory IC, meaning all data bits are transferred simultaneously through multiple lines.

Important characteristics include:

Capacity

2 KB

Word size

8 bits

Technology

EPROM

Volatility

Non-volatile

Access type

Parallel, random access

Reprogrammability

Yes, after ultraviolet erasure

Why it matters in digital electronics:

It demonstrates the difference between RAM and ROM.
It introduces the concept of address decoding and memory mapping.
It shows how firmware was stored in early embedded and computer systems.
It is a foundation for understanding later memories such as EEPROM and flash memory.

The 2716 is also historically important because it helped engineers create systems that could be updated during development without replacing hardware, saving cost and time.

Working / Process

1. Place the address on the address lines

The external processor or logic circuit sends a binary address to A0–A10.
This selects one of the 2048 internal memory locations.

2. Activate the control signals

The chip enable and output enable signals are set correctly.
Once enabled, the selected memory cell connects to the output circuitry.

3. Read or program the data

In reading mode, the stored 8-bit value appears on D0–D7.
In programming mode, a programming voltage and pulse write the data into the selected cell.
For erasure, ultraviolet light clears the chip so it can be reused.

A simple read cycle can be visualized as:

CPU/Controller -> Address lines -> 2716 EPROM -> Data lines -> CPU/Controller

The process is therefore a controlled interaction between address decoding, chip selection, and data transfer.

Advantages / Applications

Non-volatile data storage

It retains data even after power is removed, making it suitable for permanent program storage.

Reprogrammable after erasure

Unlike one-time programmable memory, the 2716 can be erased and reused, which is useful in development and testing.

Educational and historical importance

It is an excellent device for learning about memory architecture, control signals, and computer interfacing.

Applications of the 2716 include:

Storing fixed firmware in early microprocessor systems
Holding BIOS-like routines in legacy equipment
Storing lookup tables for control systems
Educational laboratory experiments in digital electronics
Prototype development where firmware changes are frequent

In older computer systems, EPROMs like the 2716 were widely used because they were reliable, easy to interface with 8-bit buses, and cost-effective for small amounts of program memory.

Summary

The 2716 is a 2K × 8 EPROM used for permanent digital data storage.
It works by selecting memory locations through address lines and outputting stored data through data pins.
It is erased by ultraviolet light and can be reprogrammed after erasure.

Important terms to remember

EPROM, non-volatile memory, address lines, data bus, chip enable, output enable, programming, ultraviolet erasure