In embedded development,insufficient storage space often happens.SPI RAM chip(also known as serial random access memory)provides a lightweight external memory expansion method for microcontroller through standard SPI interface.Compared with parallel RAM,SPI RAM takes up fewer pins and has simple wiring,which is especially suitable for designs with tight PCB space or tight pin resources.

 

 

SPI RAM relies on synchronous serial communication,and the master device(such as MCU)controls data transmission through four signal lines:SCK(clock),MOSI(master transmitter and receiver),MISO(slave transmitter and receiver)and CS(chip selection).The master device generates the clock and decides the timing of reading and writing,and the slave device responds to the instruction.This architecture enables SPI RAM chips to achieve reading and writing speeds of tens of MHz with a low pin count.Common specifications such as 23LCV512 and 47L16 have capacities ranging from several Kb to several Mb.
 

①Frame buffer in the graphical interface

②Audio sampling cache

③Batch data recording of sensor array.

④Temporary storage of network data packets
 

①Communication speed matching:SPI clock is not as high as possible.Adjust the SCK frequency according to the chip specifications,40MHz is usually the upper limit of safety,too high will lead to data dislocation.

②Chip selection control:When multiple devices share SPI bus,it is necessary to properly pull down the SPI RAM selected by CS,and pull up to release the bus after the operation is completed,otherwise conflicts may occur.

③Compatibility pre-research:SPI RAM chips from different manufacturers have differences in instruction set and standby mode.Confirm whether it is compatible with the driver library of the main control MCU before purchasing.

④Batch reading and writing optimization:byte-by-byte operation is inefficient.It is suggested to use DMA or buffer to transfer one page(e.g.256 bytes)data at a time,which can greatly improve throughput.


Keywords:SPI RAM