PSRAM Driver#

PSRAM Memory Management driver.

Introduction#

PSRAM (Pseudo Static Random Access Memory) is a random-access memory whose internal structure is based on dynamic memory with refresh control signals generated internally, in the standby mode, so that it can mimic the functionality of a static memory. It combines the high density of DRAM with the ease-of-use of true SRAM. The M4 core communicates with the PSRAM via Quad SPI interface.

PSRAM Device Configuration#

The PSRAM Driver offers configuring the following:

• Read-Write type

  • Normal: This supported only in SPI interface mode. Supports maximum frequency of 33MHz. Uses normal read and normal write command.

  • Fast: Supported in SPI and QPI mode. Uses fast read and normal write.

  • Quad IO: Supported in SPI and QPI mode. Uses fast quad read and write.

• Interface mode

  • SPI Mode (Serial IO)

  • QPI Mode (Quad IO)

• Operation frequency Source

  • Interface PLL Clock

  • ULP Reference Clock

  • SoC PLL Clock

  • M4_SOCCLKNOSWLSYNCCLKTREEGATED Clock

Linker configurations#

The text segment, data segment, bss, heap and stack can be placed in PSRAM by installing the respective components present under "PSRAM Linker Configurations" from "SOFTWARE COMPONENTS" GUI. Since PSRAM is already initiliazed in bootloader, these components can be installed and the respective segments can be placed in PSRAM without installing "PSRAM Core" component and without initializing psram from application.

Usage#

PSRAM Driver and QSPI are initiliazed by bootloader with Quad IO read-write type and QPI interface. The application is not required to reinitialize PSRAM device and QSPI unless the configurations required are different from the default set by the bootloader.

The PSRAM device handle "PSRAM_Device" of type sl_psram_info_type_t is defined "in sl_si91x_psram_handle.c".

sl_si91x_psram_uninit assumes that PSRAM was initialized with QPI mode and exits QPI mode within definition. If the PSRAM configuration in bootcode has SPI mode enabled, user is expected to comment the exit QPI mode function call in sl_si91x_psram_uninit.

To reconfigure and initliaze PSRAM, set required configurations from PSRAM Core component and call sl_si91x_psram_init within application.

Modules#

sl_psram_id_type_t

sl_psram_info_type_t