The need for memory solutions in embedded systems is rapidly increasing, in line with the surging growth of Internet of Things (IoT), artificial intelligence (AI), and 5G-enabled smart applications. Furthermore, to address the ever-increasing consumer demand for a better user experience, developers are adding more software into embedded applications. This has given rise to the emergence of serial NAND which offers higher capacity than serial NOR. As a leader in the non-volatile memory market, Macronix is the world's largest NOR flash supplier and among the world's top three SLC NAND providers.
Based on its extensive volume production experience accumulated over the years and its commitment to memory products for application in embedded systems, Macronix has excelled in product quality and production capacity. In addition, its complete range of serial NAND offerings are being enthusiastically embraced by system integrators and IC design firms.
Macronix advanced its SLC NAND product further in early 2020 by offering the compelling cost advantaged 19nm product, which is critical for NAND Flash products. In addition, Macronix operates its own fabrication facilities and so enjoys customer satisfaction for being able to maintain supply stability. According to Psyche Kuo, deputy director of product marketing at Macronix, to address the need for larger serial flash capacities by applications in embedded systems, Macronix enables improved cost and performance advantages with its 19 nm serial NAND, raising the bar in a very competitive market. Moreover, Macronix has also led the market in its initiative to remove ECC from serial NAND flash, giving SoC processors complete control over ECC functionality.
Macronix sets an example for premium quality and cost efficiency by encouraging SoC processors to handle ECC
It is a common practice for NAND flash to have built-in ECC whether it is implemented through an external ECC controller that is packaged with the NAND chip or NAND on-Die ECC. However, built-in ECC designs do not achieve significant cost saving. In fact, non-ECC memory can enable direct and clear cost benefits in embedded designs. Taking the mainstream 8 I/O SLC NAND for example, a large part of the current designs on the market leave ECC processing to SoC processors because of the compelling advantages in quality, cost and performance. This is also what drove Macronix to introduce non-ECC serial NAND solutions.
It is easier for SoC processors to perform BCH calculation for 8-bit ECC
SLC NAND technologies have advanced faster in terms of processing nodes. Thanks to stable and reliable product performance and significant savings in unit cost, SoC processors coming on the market are likely to take responsibility for ECC to accommodate increasingly large application programs in embedded systems. Like standard SLC NAND that processes 8 I/O, the SoC processor only needs to handle BCH calculations for 8-bit ECC, which is a simple for processor design teams. This means that today's serial NAND products with built-in ECC are only interim solutions and ECC handled by SoC processors will become the mainstream in the long run.
Performance boost is the main force driving the popularity of ECC being handled by SoC processors
Process technology for NAND peripheral logic lags far behind SoC process nodes so built-in ECC on NAND chips underperforms ECC handled by SoC processors. In comparing the performance between built-in ECC on serial NAND chips and serial NAND ECC handled by SoC processors, Kuo noted the latter delivers almost twice I/O performance based on 133MHz clock rate and 4KB page size. If the time the processor spends on ECC is taken into consideration, overall system performance is still 28% to 55% better than built-in ECC on serial NAND chips. This demonstrates the benefit of allowing SoC processors to carry out ECC.
SoC processors assuming ECC processing responsibility enables transparency and full processor control over serial NAND
Having SoC processors perform ECC allows them to control serial NAND to better meet system requirements on memory quality. Particularly in the case of applications that impose demanding requirements on memory lifespan, SoC processors can design in more robust ECC to increase the read cycles and program/erase cycles, which is fundamental to enhancing serial NAND endurance and reliability. For example, with SoC processors performing 12-bit ECC, serial NAND flash can withstand 1.4 more read cycles and 1.47 more program/erase cycles compared to SoC processors performing 8-bit ECC, achieving more than 40% improvement. Not only are SoC processors in full control over serial NAND ECC, they can further refine the indication mechanisms for serial NAND errors to precisely determine when to effectively move data without doing excessive and unnecessary data relocations. This also significantly improves reliability and performance. In contrast, built-in ECC on NAND chips is like a black box which the host has little control over to effectively meet system needs.
Reducing compatibility issues among serial NAND
Subject to suppliers' progress of process technology, serial NAND products on the market may be manufactured on different process nodes, including 3x nm nodes, 2x nm nodes, or the latest 19nm node. They also come with different ECC capabilities, resulting in wide-ranging serial NAND EEC specifications on the market. This makes it difficult for SoC processors to implement a uniform design to decide when to move data from a bad block to a good block. More often than not, SoC processors need intricate designs to work with built-in serial NAND EEC. In addition, serial NAND products with built-in EEC have different ECC protection ranges due to different suppliers' definitions of spare areas under the page structures so it is difficult to control in software So having SoC processors taking over ECC eliminates the hassle of handling different ECC protection ranges because SoC processors can make the decision on the ECC protection range. To summarize, when SoC processors have full control, serial NAND compatibility is of little concern, making processor design easier and more straightforward.
Suppliers and customers of SoC and serial NAND all benefit from the trend to have ECC handled by SoC processors
Having SoC processors take over ECC allows them to be in full control so this is an ideal solution that creates an overall, winning solution. However, the serial NAND market is still full of diverse ECC specifications developed during its transition period. In view of this, Kuo suggests that developers have the processor's initial boot loader disable serial NAND's internal ECC if they decide to have the processor handle ECC. This will allow the processor to use the same firmware to work with different serial NAND products, regardless of whether built-in ECC exists, thereby maximizing system flexibility.
NAND flash lifespan can be increased with SoC processors having the ability to decide on the ECC strength and the proper time to move data. This is why Macronix is able to immediately win support from the largest chip maker in Taiwan and China as a result of launching its advocacy campaign promoting SoC processors handling ECC. Aside from cost and performance advantages, developers will have a complete grasp of system integrity and security, thereby fully realizing the value of next-generation SoC design.
Home gateways, as an example, is a popular product that combines a modem and a home router into a single smart home device. It enables the Gigabit Ethernet Passive Optical Network (GPON) to expand into broadband and smart home markets. As smart home applications and services generally require large amounts of image processing and data transmission, developers of home gateway SoC chips make use of digital signal processors (DSP) and application-specific integrated circuit (ASIC) architectures to cope with a diversity of data processing needs. They also incorporate multiple data security implementations, robust virtual private network (VPN) functionality, cryptographic algorithms and a slew of other technologies. SoC capability and performance are rapidly growing with advancements of semiconductor process technologies. SoC chips need higher flash memory capacity to store program code and data while requiring flash memory to deliver optimal performance and reliability. Incorporating serial NAND that hands over ECC processing to SoC processors will boost system performance and contribute to the success of network communication SoC products.
Macronix's 19nm serial NAND is well positioned in niche and high-value-added products. By removing built-in ECC from its 19nm serial NAND memory products, Macronix allows customers to fully enjoy the high-performance advantage brought by cost saving and processor control. This is in line with Macronix's strategy to move toward customization, which enables it to effectively grasp diverse market needs. Macronix offers a complete lineup of 3V serial NAND available in 1/2/4Gb capacities that is now ships. These products have been used in SoC chips for network communication devices and consumer electronics. Long-term development potential for these products looks promising.
Kuo spoke candidly that it may take a considerable time for the business model of embedded systems to make this necessary transition. To meet the needs of the market that lack the R&D resources, Macronix still maintains some serial NAND product lines with built-in EEC. With broad product solutions for the transition period in place, its ability to maintain stable supply, quickly adjust production capacity, and strengthen necessary partnerships, Macronix will help expand the use of serial NAND into more embedded applications.
Psyche Kuo, deputy director of product marketing at Macronix
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