Miscellaneous notes on SRAM, PSRAM, and SPI FLASH

fish001

Miscellaneous notes on SRAM, PSRAM, and SPI FLASH [Copy link]

My current work is mainly to develop and design products on the RDA5981 platform. During the design process, I came into contact with SRAM, PSRAM, and SPI FLASH, so I took this opportunity to sort out the relevant knowledge in this area. The following content is rather messy, mainly recording the concepts of SRAM, PSRAM, DRAM, SDRAM, the introduction of PSRAM, and some knowledge points that need to be mastered for SPI FLASH. RDA5981 has 448KByte of SRAM Question: In actual applications, how are SRAM resources allocated? What is the difference between SRAM and DRAM? Extension: SRAM: Static RAM, static random access memory - SRAM exists inside the MCU, with a relatively small capacity, generally KB~MB, and fast speed; PSRAM: Pseudo static RAM, refers to pseudo static random access memory; DRAM: Dynamic RAM, dynamic random access memory; SDRAM: Synchronous Dynamic RAM, synchronous dynamic random access memory - used for applications with large code, complex algorithms, and operating systems. SDRAM is independent of the MPU and can choose the size of RAM according to the application. Generally, SDRAM is used externally, with a relatively large capacity, generally MB~GB. DDR is a type of SDRAM. 1. What is PSRAM? PSRAM stands for Pseudo static random access memory, which refers to pseudo static random access memory; it uses DRAM technology and technology to implement RAM devices similar to SRAM. SRAM uses a 6T architecture, while DRAM uses a 1T1C architecture. Therefore, for the same volume, the capacity of PSRAM can be made larger and the price is relatively lower. 2. In what situations will PSRAM be used? Why is PSRAM used? ①PSRAM is an ideal choice for many portable products that require a certain cache capacity, especially for data-intensive, burst access, and data algorithm (such as FFT, DFT, etc.) applications ②PSRAM has the advantages of simple SRAM circuit interface and large DRAM capacity. At the same time, the refresh circuit is integrated into the chip, combining the advantages of SRAM's simplicity and ease of use and DRAM's large capacity. It has been supported and recognized by engineers and customers and is widely used; ③Traditional PSRAM is a parallel interface, which consumes more MCU/SoC I/O pin resources. IPUS has launched a serial PSRAM that supports SPI/QSPI interface, providing a memory expansion method for MCU/SoC that does not have a parallel RAM expansion interface. 3.What are the advantages of PSRAM over DRAM/SRAM? Comparison with SRAM ① Compared with SRAM (using 6T technology), PSRAM uses 1T+1C technology. PSRAM has much larger capacity and lighter volume than SRAM; ② PSRAM is much cheaper than SRAM and has a more competitive price; ③ The I/O interface protocol of PSRAM is the same as SRAM; Comparison with DRAM ① PSRAM uses self-refresh, which can save the data stored inside without refreshing the circuit; while DRAM needs to be refreshed and charged every once in a while, otherwise the internal data will disappear, so PSRAM has higher performance; ② PSRAM has a simpler data access interface than DRAM; 4. What are the interfaces applicable to PSRAM? The main interfaces applicable to PSRAM include SPI, Quad SPI, etc.