e-MMC memory

Since bidding farewell to the era of feature phones, various terminal products such as smart phones and tablet computers have continued to gain popularity. Storage devices, as key components of smart hardware devices, are also evolving and iterating with market demand. The form of storage devices in smart phones has also changed. Advance with the times. Mobile devices such as smartphones and tablet computers are booming. Any component may affect the overall performance and experience of the phone, such as the processor, memory, flash memory, screen, and so on. Compared with processor chips, the importance of storage performance in smartphones has gradually become more prominent in recent years. With the improvement of processor performance and the improvement of the picture quality of mobile games, the bandwidth of storage devices has become more important.

??In addition, with the differentiated needs of consumers, the compatibility of similar devices with different configurations has become increasingly important, so new types of memory represented by eMMC (embedded multimedia memory card) and UFS (universal flash memory storage) have emerged, which solves the past When using NAND FLASH as a storage medium, there is a huge cost reduction in read-write control, fault management, system upgrade and maintenance. eMMC encapsulates NAND FLASH and NAND FLASH controllers with standard interfaces, and adopts 8bits standard parallel interface to the outside world. Before 2018, it was widely used in consumer electronics products such as smartphones, tablets, and cameras. UFS is a new generation of universal flash memory standard after eMMC. It uses high-speed serial communication for data transmission. Compared with eMMC, the transmission speed has been further improved. In 2017, it has also begun to be used in smart phones and other fields. Already, the smartphone flash memory market is almost dominated by UFS. The share of eMMC is decreasing year by year, and currently only a small number of low-end devices are used.

??Both eMMC and UFS are commonly used flash memory specifications such as mobile phones, tablets, memory cards, etc., and both are standards for mobile flash, and their interface technologies are quite different. But they all have the following characteristics:

??●Proper capacity

??●Proper performance

??●Extremely sensitive to power consumption and volume requirements

??●Only need to follow certain interface standards

??Relying on the MMC standard, eMMC uses an 8-bit parallel interface, uses eight channels to transmit data, half-duplex mode, and cannot be read during storage. The theoretical maximum value of the eMMC 5.1 standard can reach up to 400 MB/s. UFS replaces the parallel interface with a high-speed serial interface, adopts a full-duplex mode, can read and write at the same time, the transmission data efficiency and bandwidth of each channel are much higher than emmc, the application of smart phones has entered UFS3.0. Figure 1 shows the comparison of UFS and eMMC reading speed, bandwidth, etc.

With the development of technology becoming more and more mature, mobile devices have been able to derive different levels of products to meet the needs of different consumers. CPUs are divided into low, medium and high-end, and memory also has the concept of the so-called memory class. Consumer electronics products at different price points, Various types of memory with different storage capacities, computing speeds, and unit prices must be properly allocated to achieve maximum economic benefits.

??With the improvement of the basic performance of mobile devices, UFS flash memory with more development potential is obviously more suitable for mobile devices than eMMC flash memory, and is more in line with the development process of mobile devices. In the development of smart phones, the flash memory configured gradually has an absolute advantage from eMMC. The dominant position has become UFS dominating the mid-to-high-end market. In terms of price, Emmc is generally used for low-end phones, and UFS is used for high-end flagship phones. At present, UFS 3.0 has a firm foothold in high-end flagship phones, and UFS 2.1 is gradually sinking to thousand yuan phones, and eMMC's share in the mobile phone market has been squeezed smaller and smaller. However, the target application of eMMC design is consumer electronic products with higher storage capacity requirements. It can gradually turn to face smart screens, tablets, cameras, and building security. The broad market has great potential, such as voice recorders, optical modems, set-top boxes, AR/VR, smart watches, car navigation, smart rearview mirrors, game consoles and other fields are even more popular. Its characteristics and cost performance determine that it will not withdraw from the stage of history for the time being.

In automotive electronics, whether traditional fuel vehicles or new energy vehicles, the design of virtual dashboards will only become more demanding. With the promotion of new energy vehicles and the requirements of vehicle replacement, eMMC also has a large market demand.

??In the tablet market, the response rate is far less demanding than that of mobile phones. In the next one to two years, eMMC will also be seen in normal tablet hardware configurations.

??In addition, with the layout of new infrastructure, compared with the current 40 million 4G base stations in China, the current number of 5G base stations is far below the requirements for large-scale popularization of 5G mobile phones. The three major operators need to purchase a large number of eMMC chips for 5G. Base station construction, so eMMC has a large market share in 5G construction.

??With the gradual advancement of new rural construction year by year, the demand for eMMC in the security market remains stable, and with the popularization of 5G, there will be more and more renovation projects of smart buildings, and eMMC will be revived by the mobile phone market.

??The smart home market is expanding year by year with only one goal-user experience. Smart screens will be used more and more in home upgrades. User experience is extremely important. The use of eMMC will make a significant contribution to its performance improvement. As shown in Figure 3, the application scenarios of smart homes are highly mature and sensitized, and eMMC is indispensable, and the gateway is inevitable.

??The eMMC market is widely used, which is the result of technological development and the inevitable result of the continuous improvement of user experience requirements for interactive products.

??eMMC's arrival on the stage of history stems from the requirements of similar designs in different configurations of smartphones, and from the design pressure of updating. Before the advent of eMMC, the built-in storage of mobile phones mainly relied on a single Nand Flash. As shown in Figure 4, compared with eMMC: The interface and timing of Nand Flash are not standard. NandFlash is actually a category rather than a fixed product, and the products of various manufacturers cannot be directly used.

??Nand Flash has too many pins and large volume. Therefore, Nand chips cannot be used in small products with high volume requirements, which greatly limits the direct use of Nand.

??The capacity of Nand Flash cannot be flexibly controlled. With the Nand chip of the same manufacturer, the pin interface and package of different capacity can also be different, and the design and production of the same series of products with different capacities are more troublesome.

Nand Flash has bad blocks, so people invented bad block management technology to mark bad blocks and avoid using them.

??Nand Flash requires ECC (error checking). Sometimes some specific bits in some blocks will be flipped when they are read after a period of time. The original value stored here is 1 and the result is read as 0. The solution is ECC. When we write, we first calculate the ECC value of the data with an algorithm, and store the ECC value and the data in the block into Nand. When it is to be read, the data in the block and the ECC are read together, and then the ECC of the data in the block is calculated by the same algorithm, and the ECC is compared with the read ECC. If they are the same, it is considered that the data has not been inverted. Both bad block management and ECC need to configure additional CPU to help use Nand Flash.

??In view of the above problems, it caused resistance to the application of Nand Flash in mobile devices, so eMMC came on the scene. The emergence of eMMC solves the development defects of NAND FLASH. eMMC encapsulates NAND FLASH and NAND FLASH controllers and standard interfaces into a BGA packaged chip. The eMMC controller is responsible for the bad block management, ECC verification, and erasing of FLASH. Balance and other operations, while adopting a unified interface and standard specifications, facilitate the secondary development of the product, and have the advantages of good compatibility and easy upgrade. The standard is embodied in at least three aspects: physical packaging, hardware level and pin position, and software timing. Therefore, all EMMC chips can be directly replaced under a given package, regardless of manufacturer and capacity, which is convenient for purchase and replacement. Therefore, the difficulty of product design and stocking is greatly reduced, and the cost is greatly reduced. Figure 5 is a block diagram of eMMC.

The biggest advantage of eMMC accelerates the update speed of new products, reduces research and development costs, and shortens the development cycle of new products. eMMC is an embedded memory specification designed for smart phones. It is an extension of the external memory card MMC. After eMMC has also spread to the tablet PC (Tablet PC) application field.

The eMMC chip partition is shown in Figure 6. There are three partitions in the chip, namely Boot1, Boot2 and User Area.

??1. BOOT1&BOOT2 ROM

??The main function of this partition is designed to support the emmc boot system. The data of this partition can be read out through a very simple protocol after the EMMC is powered on. At the same time, each platform can support the ROM code to load the contents of the EMMC BOOT partition into the SRAM inside the SOC after power on implement.

??2. RPMB partition

??RPMB is the abbreviation of Replay Protected Memory Block. It uses HMAC SHA-256 and Write Counter to ensure that the data stored in the RPMB is not illegally tampered with. In practical applications, the RPMB partition is usually used to store security-related data, such as fingerprint data, secret keys related to secure payments, and so on.

??3. General Purpose Partition 1～4

??This area is mainly used to store system or user data. The General Purpose Partition will only exist after the chip needs to be actively configured after it leaves the factory.

??4. User Data Area

??This area is mainly used to store system and user data. UDA partitions are usually divided in more detail. In the Android system, BOOT/system/userdata and other partitions are usually divided into this area.

??MMC is technically better than Nand, but it is indeed cheaper than Nand. One of the reasons why EMMC is cheap is because of standardization. Standards can be mass-produced, mass-circulated, mass-loaded, and mass-used. Another big reason why EMMC is cheap is the internal use of MLC instead of SLC. MLC with the same capacity is cheaper than SLC, but with higher capacity, bad blocks and flips occur. Therefore, the widely used Nand are all SLC. When MLC Nand is used directly, the cost of NAND CONTRAL is higher, and EMMC solves this problem. Built-in control The device manages MLC Nand well, so it can be large in capacity, easy to use, and cheap.

??As one of the leaders in the non-volatile memory packaging substrate market, HOREXS has mastered a series of eMMC and other memory chip packaging substrate manufacturing technology and experience to meet the needs of customers for various capacity storage and high reliability applications. HOREXS's years of experience in the manufacturing and management of flash memory packaging substrates combined with its advanced NAND flash packaging substrate manufacturing technology makes this type of product have a very high quality yield rate and very stable, forming a reputation for winning customers with technology, and the market prospects are very promising. good.