SRAM, PSRAM, SPI Flash Miscellaneous

The current work is mainly in the RDA5981 platform for product development and design, in the design process to contact the SRAM, Psram and SPI Flash, so take this opportunity to collate the relevant knowledge.
The following is a messy, mainly recorded the concept of SRAM, PSRAM, DRAM, SDRAM and the introduction of PSRAM, and the SPI Flash need to master some of the knowledge points. SRAM

RDA5981 has 448KByte SRAM.

Questions
In the actual application, the allocation of SRAM resources is how to allocate.

The difference between SRAM and DRAM.

Extension:
Sram:static RAM, static random access memory-–sram exist in the MCU, the capacity is smaller than the general kb~mb, fast;
Psram:pseudo static RAM, which refers to pseudo-static random memory;
Dram:dynamic RAM, dynamic random access memory;
sdram:synchronous Dynamic RAM, synchronous dynamically random access memory--applied to the code large, the algorithm is complex, with the operating system, SDRAM independent of the MPU, can choose the size of RAM according to the application situation, general external use SDRAM, the capacity ratio is large, General Mb~gb,ddr is a kind of SDRAM. PSRAM

What

1.PSRAM is.
Psram full name pseudo static random access memory, refers to pseudo-static RAM, it is the process and technology of DRAM, similar to SRAM-like memory devices. SRAM uses a 6T architecture, and the DRAM uses the 1T1C architecture, so the same volume, psram capacity can be made larger and less expensive.
2. Under what circumstances will the Psram be used. Why do you use Psram? The
①psram is an ideal choice for many portable products that require a certain amount of cache capacity, especially for data dense, burst access, applications involving data algorithms such as FFT, DFT, and so on
②psram not only have the advantages of compact SRAM circuit interface, Also has the characteristics of large dram capacity, while the Flash circuit integrated into the chip inside, both easy to use SRAM, the advantages of large DRAM capacity, the vast number of engineers and customers to support and recognition, and widely used;
③ traditional psram are parallel interfaces and consume more mcu/ The I/O pin resource for the SOC. IPUs introduces a serial psram that supports the SPI/QSPI interface, providing a way for memory expansion for MCU/SOC without a parallel RAM expansion interface. What are the benefits of
3.PSRAM and Dram/sram?
compared to SRAM
① with SRAM (using 6T technology) compared to Psram using 1t+1c technology, Psram capacity is much larger than SRAM, the volume is lighter;
②psram price is much cheaper than SRAM, the price is more competitive;
The ③psram I/O interface protocol is the same as SRAM,
compared to DRAM
①psram uses self-flushing (Self-refresh), does not need to refresh the circuit to save its internal stored data, and dram every time, to refresh the charge once, Otherwise the internal data disappears, so the Psram has higher performance, and the
②psram has a more streamlined data access interface than DRAM;
4.PSRAM is available for the interface.
Psram The main applicable interface includes SPI, Quad SPI, etc. SPI FLASH

Rda5981c has 4MB of built-in SPI Flash
in the reference document, "RDA5981 Flash Introduction", "Rda5981_flash zoning Manual and Ota interface _v2.2" Two documents in detail on the flash partition, Explanation of the relevant partitions and information such as the Flash Operation interface.
Knowledge Points:
1. Memory Standard SPI Interface PIN information:

2. General connection Considerations
Pin8 is VCC: filter capacitance to ground
Pin4 is GND: Connect To
Pin3, 7: Pull-up
other four signal pins: Connect directly to the main device

take the time to read two copies of the SPI Flash data sheet.