1. How to convert Analog signal into digital?
Ans. Analog Signal(input) → Sample & Hold circuit → Quantization → Encoding → Digital Signal (output)
Sampler takes samples i.e. records value of the analog signal at a specified time and this random values of sampled signal is quantized to defined levels and these levels are encoded by defined number of bits and thus digital signal is obtained.
2. In 8085 microprocessor which signal separates address lines and data lines.
Ans. Address Latch Enable (ALE) is the signal that separates the address and data lines. 8085 processor has 16 address lines for 16 bit address of a memory location. Out of this 16 address lines 8 address lines are solely dedicated to transfer 8 higher order address bits while the remaining lower order 8 bits of the address are sent through another 8 lines multiplexed with the 8 bit data lines.
It is the control signal ALE to be sent by the processor in appropriate time to indicate the operation of this 8 bit multiplexed bus whether it will be used to send the lower order 8 address bits or to send the 8 data bits.Making ALE control HIGH the multiplexed 8 bit bus will act as address bus while making ALE control LOW the same 8 bit multiplexed bus will act as data bus. Thus, ALE = 1 makes the address latched i.e. latch enable and ALE = 0 makes the adress bus disable but making it data bus enable.
3. Why flash type memories are preferred over EEPROM?
Ans. EEPROM memories are slow as compared to flash memories because in EEPROM, a single read or write of memory location can be done in single operation whereas in flash memory multiple memory location can be erased or written in one programming operation.
4. How the resolution is increased in floating point representation of number?
Ans. More the number of bits used in fraction part, better will be the resolution. As resolution means smallest value that can be represented so more number of bits guarantee more resolution.
5. Which one has fast erase and write time ,NOR flash or NAND flash?
Ans. NAND flash, that’s why NAND is most widely used universal gate for designing all other logic operations.
6. Give advantages of fixed point representation.
Ans. Cost and complexity of algorithm is less in fixed point representation. So it is suitable for time domain filtering.
7. what are advantages of floating point representation over fixed point representation?
Ans. Quantization error is small and dynamic range is high for floating point representation so it is suited for frequency domain algorithm i.e. FFT etc.
Resolution of floating point is also high which proves as an advantage.
8. An IC has name 74LSXXX . What do you mean by LS?
Ans. LS means low Schottkey TTL(transistor transistor logic) IC. Schottkey TTL gates are used to improve the speed of gates.
9. What do you mean by aperture jitter & this term is associated with which circuit?
Ans. The RMS variation in t ime of the sampling instant caused by jitter in the sample-hold command signal is known as Aperture Jitter it is associated with sample and hold circuit.
10. What do you mean by Acquisition Time in sample and hold circuit?
Ans. The length of time during which the S/H must remain in the sample mode in order for the HOLDS capacitor to acquire a full scale step input.
11. What do you mean by sampling jitter?
Ans. Sampling jitter is the error in placement of each clock edge controlling the point when sampling begins. In analog-to-digital and digital-to-analog conversion of signals, the sampling is normally assumed to be periodic with a fixed period—the time between every two samples is the same. If there is jitter present on the clock signal to the analog-to-digital converter or a digital-to-analog converter, the time between samples varies and instantaneous signal error arises. The error is proportional to the slew rate of the desired signal and the absolute value of the clock error. The effect of jitter on the signal depends on the nature of the jitter.
12. What is an INHIBIT Gate?
Ans. It is basically an AND gate with one of its input negated by an inverter as shown below.
13. A flip-flop is which type of Multivibrator: Astable, Monostable or Bistable.
Ans. A flip-flop is Bistable multivibrator since it has both of its output states stable. Bistable multivibrator, in which the circuit is stable in either state. It can be flipped from one state to the other by an external trigger pulse. This circuit is also known as a flip-flop.
TR1 and TR2 are trigger to change the state.
14. What is race around condition and how it is avoided?
Ans. In flip flops when clock pulse is applied, output changes when input changes. But in JK flip flop, when J=1,K=1 , at each clock pulse output changes(output toggles) without any change in the input.This is called RACE AROUND CONDITION.It occur for J = K = 1 for level triggering. The remedy is to use edge triggered J-K flip-flop which is also known as master slave J-K flip-flop.
The input signals J and K are connected to the gated “master” SR flip flop which “locks” the input condition while the clock (Clk) input is “HIGH” at logic level “1”. As the clock input of the “slave” flip flop is the inverse (complement) of the “master” clock input, the “slave” SR flip flop does not toggle. The outputs from the “master” flip flop are only “seen” by the gated “slave” flip flop when the clock input goes “LOW” to logic level “0”.
When the clock is “LOW”, the outputs from the “master” flip flop are latched and any additional changes to its inputs are ignored. The gated “slave” flip flop now responds to the state of its inputs passed over by the “master” section.
Then on the “Low-to-High” transition of the clock pulse the inputs of the “master” flip flop are fed through to the gated inputs of the “slave” flip flop and on the “High-to-Low” transition the same inputs are reflected on the output of the “slave” making this type of flip flop edge or pulse-triggered.
Then, the circuit accepts input data when the clock signal is “HIGH”, and passes the data to the output on the falling-edge of the clock signal. In other words, the Master-Slave JK Flip flop is a “Synchronous” device as it only passes data with the timing of the clock signal.
15. What is the difference between PLA and PAL?
Ans. PLA and PAL are type of ROMS, in PLA both And and OR gates are programmable but in PAL only And gates are programmable which makes the chip less complicated and enable us to implement wired AND-OR product terms.
16. What is figure of merit in logic families?
Ans. In logic families figure of merit is product of propagation delay and power disspated. It should be as low as possible. The product of the signal propagation delay times the average power dissipation has been used as a figure of merit for digital systems in much the same way as the gain times bandwidth product has been used to evaluate and compare devices intended for linear circuit applications.
17. What is the condition for an RC circuit to work properly as Integrator?
Ans. For an RC circuit to work properly as integrator RC ≥ 10 T. T is pulse width of input waveform VIN.
18. What is the difference between emulator and simulator?
Ans. Simulator is just software which act like hardware inside that we can see all electronic components and connect them in different manner to get output while emulator is actual hardware.
In computing, an emulator is hardware or software that enables one computer system (called the host) to behave like another computer system (called the guest). An emulator typically enables the host system to run software or use peripheral devices designed for the guest system. Emulation refers to the ability of a computer program in an electronic device to emulate (or imitate) another program or device.
19. What do you mean by interfacing? Explain it.
Ans. Interconnection of devices belonging to different domain is known as interfacing. For example computer works only on discrete numbers. So an analog signal has to be first converted into discrete samples before being fed to computer.
A boundary across which two independent systems meet and act on or communicate with each other. In computer technology, there are several types of interfaces.
- user interface - the keyboard, mouse, menus of a computer system. The user interface allows the user to communicate with the operating system.
- software interface - the languages and codes that the applications use to communicate with each other and with the hardware.
- hardware interface - the wires, plugs and sockets that hardware devices use to communicate with each other.
20. How microprocessor functions without internal memory?
Ans. Microprocessor consist of address, data and control buses with some internal registers to process the task through external memory by using certain commands to access memory locations of the external memory.
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