Qualcomm Interview Question Bank continued from Part 3…
Q : What is race-around condition? What is the solution for it?
A : In JK flip-flop, when both J and K are 1, the state (output) of the flip-flop will oscillate between 0 and 1 resulting to uncertainty in the state of the flip-flop at the end of the clock pulse. This problem can be solved by using edge-triggered flip-flop or Master-Slave JK flip-flop.
Q : What is setup and hold time?
A : Setup time is the amount of time before the active edge of clock during which data should remain stable. Hold time is the (minimum) time after the active edge of the clock during which the data must be held stable.
Q : What is cache memory? What are its different types?
A : Cache memory is a temporary memory located inside or very close to CPU (Central Processing Unit) chip. It operates very fast (faster than RAM also) and stores the most frequently used data or instructions used by CPU. It is very expensive and therefore is limited in storage capacity. The types of cache memory are mainly of three types,
Level 1 (L1) – It has the smallest capacity (upto 128 KB), built directly into the processor chip and also known as primary internal cache.
Level 2 (L2) – Has more capacity (upto 8 MB) but is slower than L1 cache.
Level 3 (L3) – This is slower than both L1 and L2 cache memories. It is built separately from processor on the motherboard and can store upto 8-10 MB.
Q : What is phase-shift oscillator?
A : Phase-shift oscillator is a linear electronic oscillator circuit that consists of an inverting amplifying element (like op-amp or transistor) and produces sine wave as output. It has a positive feedback circuit of resistors and capacitors connected in a ladder network which shifts the phase of the circuit by 180 degrees. It is often used in audio applications.
Q : What is the advantage of Johnson counter over Ring counter?
A : Johnson counter uses only half the number of flip-flops as compared to standard Ring counter for the same MOD. So, a Johnson counter that has n number of flip-flops is said to be MOD-2n counter. Johnson counter is a modified Ring counter.
Q : What is throughput?
A : Throughput is the maximum data rate which is available to a user using a network. A channel may have a capacity of say, 5 Mbps but the throughput would be lesser than 5 Mbps.
Apart from DSP and other core ECE concepts, Qualcomm also asks computer science related questions on topics like OOPS, DS and algorithms depending upon the profile. Many online resources are available to refer the said topics.