Flash Memory and Flip-Flops: Comprehensive Insights
What is Flash Memory?
(Asked in MDU BCA 2023, 2022, 2015, 2021, 2017)
Flash memory is a type of constantly powered, nonvolatile memory. This means that it stores information on a silicon chip in a way that does not need power to maintain the information in the chip. It can be erased and reprogrammed in units of memory called blocks. It is a variation of Electrically Erasable Programmable Read-Only Memory (EEPROM), which, unlike flash memory, is erased and rewritten at the byte level, which is slower than flash memory updating. Normal EEPROM only allows one location at a time to be erased or written, meaning that flash memory can operate at effectively higher speeds when the system uses it to read and write to different locations at the same time.
Flash memory is often used to hold control code such as the Basic Input/Output System (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written to in block (rather than byte) sizes, making it easy to update.
Flash memory offers fast read access times and solid-state shock resistance. These characteristics explain the popularity of flash memory for applications such as storage on battery-powered devices like cellular phones and PDAs.
What are Flip-Flops?
General Characteristics and Applications
A flip-flop is a circuit capable of storing one bit of information, either 1 or 0, based on the inputs applied to it. It is a data storage system used to store information in sequential logic systems. A flip-flop has two stable states: one is “set” or 1, and the other is called “reset,” “clear,” or 0. There are two input lines, two output lines, and a clock line. The state of the output at any instant depends upon the past outputs and the data input present at that instant.
Flip-flops are combined to form counters, shift registers, and various memory devices.
Characteristics of Flip-Flops
There are many types of flip-flops, but all share the following characteristics:
- A flip-flop is a basic memory element.
- A flip-flop is a bi-stable multivibrator.
- A flip-flop circuit has two stable states: one is “set” or 1, and the other is called “reset,” “clear,” or 0.
- It continues to remain in either of the states until some triggering signal is applied to change its state.
- A flip-flop can have one or more inputs. These inputs cause the flip-flop to switch back and forth between its possible output states.
- The two output signals, Q and Q’, are always complementary to each other (i.e., if Q = 1, then Q’ = 0, and if Q = 0, then Q’ = 1).
- It serves as a storage device. It stores 1 when its Q output is 1 and stores 0 when its Q output is 0.
Applications of Flip-Flops
There are a number of applications of flip-flops. Some of them are listed below:
- Data Transfer: The data stored in one flip-flop can be easily transferred to another flip-flop. The data can be transferred serially (i.e., bit by bit) or in parallel form (i.e., all bits at a time from the Q outputs of each flip-flop).
- Digital Counting: A number of flip-flops can be connected to count pulses electronically. A single flip-flop can count up to 2 pulses; two flip-flops can count up to 22 = 4 pulses. Similarly, n flip-flops can count up to 2n pulses. Flip-flops can be used to count up, down, or up/down.
- Basic Building Block: A flip-flop is used as a basic building block in sequential circuits such as counters and registers.
- Frequency Division: Flip-flops are used for frequency division. One flip-flop can divide the frequency by half.
- Data Storage: Data storage is the basic feature of digital systems. Flip-flops are used for parallel as well as serial data storage.