Summary of digital IC design written test questions (four): some basic knowledge points

1. Component voltage threshold

General voltage threshold refers to the threshold value of the transistor of the component. The higher the threshold value, the slower the speed, but the lower the power consumption.Therefore, according to the specific situation, high-threshold components can be used to reduce power consumption where high-speed operation is not required, and low-threshold components can be used to ensure speed where high-speed operation is required, so as to achieve low power consumption without affecting the operating frequency.the purpose of the design.

2. What is the 28nm process node?

The general process node refers to the width of the gate of the MOS transistor;

3. What is the difference between pre-imitation and post-imitation?

Pre-simulation refers to the simulation before placement and routing, while post-simulation refers to the simulation after placement and routing, and the results of post-simulation are closer to the real data;

4. What is the difference between the Harvard structure and the von Neumann structure?

Harvard structure: programs and variables are stored separately

• Advantages: easy to manage, not easy to crash;
• Disadvantages: Relatively low resource utilization;

Von Neumann structure: programs and variables are stored together

• Benefits: Make the most of resources
• Disadvantage: The program and variables are put together. If the program runs away, the original program may be read and written as a variable, which will cause the driver and the Harvard structure to store the program variables separately. Even if the program runs away, it will only beAffect the running order of the program, will not change the program itself and cause a crash.

5 . What are little-endian and big-endian?

little-endian: little endian, high byte data is stored in high address bits, low byte data is stored in low address bits;
big-endian: big endian, high byte data is stored in low address bitsAddress bit, the data of the low byte is stored in the high address bit;

As shown in the figure, if the data is read in little-endian mode, the data is "9abc56781234"; if it is read in big-endian mode, the data is "123456789abc".

6.set_multicycle_path in sdc

In digital IC design, we hope that most operations can be completed within one clock cycle, otherwise we need to insert registers; but we can allow some operations to be completed in multiple cycles, set_multicycle_path is for multi-cycle operationsTiming constraints;

References

[1]CSDN: In-depth explanation of set_multicycle_path multi-cycle constraints - theoretical articles
[2]CSDN: Detailed Explanation of Big Endian and Little Endian