System-on-Chip (SoC) Design Elements Guide

A System-on-Chip (SoC) is an integrated circuit that contains all the required electronic circuits for a fully functional system. We’ve already discussed the basics of SoCs and why they are so critical for the next generation of computing and established many advantages from miniaturization to power efficiency to production methods. However, in this article, we’ll be delving into what exactly goes into creating a System on Chip design. 

Everything Integrated in an SoC

SoCs seek to integrate as many computer components as possible onto a single piece of hardware. This integration typically includes the CPU, GPU, memory interfaces, possible cellular communications methods, and other components onto a single die. 

Let’s take a close look at each. 

• SoCs require at least one processor core but generally have multiple. Processor cores include a microcontroller, microprocessor, digital signal processor (DSP), or an application-specific instruction set processor (ASIP). Whether they contain single-core or multiple processor cores, SoC process cores generally use RISC instruction set architectures. This architecture requires less digital logic and less power consumption and area on board. SoCs often use ARM architectures as it is available as an IP core and may be more efficient than x86 architecture. 
• The second critical SoC component is memory blocks through a memory or cache hierarchy. Common memory technologies for SoCs include read-only memory (ROM), random-access memory (RAM), Electrically Erasable Programmable ROM (EEPROM), and flash memory. RAM subtypes include faster static “SRAM” and slower and cheaper dynamic “DRAM.” In the case of a cache hierarchy, SRAM structure is used for processor registers, whereas DRAM is used for main memory.
• SoCs must interface with the outside world through a series of external interfaces generally used for communication protocols. Examples include USB, FireWire, USART, SPI, Ethernet, HDMI, and I2C, depending on the application. Other wireless networking protocols such as BlueTooth, Wi-Fi, and RFID capabilities may also be supported. 
• SoCs also contain various supporting circuitry for functionality, including voltage regulators and power management circuits. Other timing circuitry includes phase-locked loop control systems, clocks and timers, oscillators, power-on reset generators, and analog-to-digital converters (ADCs).

System-on-Chip Design Workflow

Designing SoCs involves hardware and software to control the processor, peripherals, and interfaces. A strong design workflow develops hardware and software simultaneously in an architectural co-design method.

Concerning hardware, as with integrated circuit design in general, many SoCs are developed using hardware component IP core specifications, known as blocks. Hardware blocks are created using EDA tools and can be classified into the following categories:

• Hard IP cores are hard layouts using physical design libraries but are technology dependent and may lack flexibility.
• Soft IP cores include VHDL/ Verilog code with functional descriptions of IPs, making them more flexible and reconfigurable but requiring synthesis and verification before implementation.
• Firm IP cores strike a balance between the two and are provided as netlists to specific physical libraries after synthesis. 

On the software side, SoCs are designed with high-level programming languages (MATLAB, C++, etc.) and are converted to RTL designs through high-level synthesis tools. These algorithmic synthesis tools allow designers to model and synthesize the system, circuit, software, and verification levels in a single language. 

After architecture is defined, new hardware elements are written and synthesized into register transfer level (RTL), defining the circuit behavior and then connected in HDL, creating the full SoC design.

The SoC must be verified for validation before being manufactured in a foundry, in a process known as functional verification. The verification process accounts for a large portion of the chip design life cycle —up to 70%. Once the chip is fully verified to work as intended, it is sent to the foundry for mass production.