MR25HXXX

This library aims to support the following MRAM memory chips from Everspin Technologies for Arduino core:

Name	Size	Datasheet	Tested
MR25H128	128 Kb	link	Yes (on Arduino Nano)
MR25H256	256 Kb	link	No
MR25H10	1 Mb	link	No
MR25H40	4 Mb	link	No

Examples

See examples/ folder.

Documentation

Classes

Available classes are:

• MR25H128
• MR25H256
• MR25H10
• MR25H40

The first two chips only need two bytes (uint16_t) to address all the memory on the chip. The last two require three bytes (uint32_t). The following documentation uses addr_t to describe the addressing datatype.

Memory Protection Modes

The MR25HXXX family supports four different memory protection modes:

Mode	Info
MR25HXXX::ProtectionMode::PROT_NONE	Every memory cell can be written
MR25HXXX::ProtectionMode::PROT_UQ	Only the first 3/4 of memory can be written
MR25HXXX::ProtectionMode::PROT_UH	Only the first 1/2 of memory can be written
MR25HXXX::ProtectionMode::PROT_ALL	No memory cell can be written

Methods

Each class provides the following methods. Look into source code for more documentation.

Get total number of bytes in memory:

• addr_t memorySize()

(Un-)Initialize the mram chip object:

• void begin()
• void end()

Methods for direct status register manipulation (not recommended to do manually):

• StatusRegister readStatusRegister()
• void writeStatusRegister(StatusRegister sr)
• void enableWriteStatusRegister()
• void disableWriteStatusRegister()
• bool isStatusRegisterWritable(StatusRegister sr)
• bool isStatusRegisterWritable()
• bool isWriteEnabled()

Get/set memory protection mode:

• ProtectionMode getProtectionMode(StatusRegister sr)
• ProtectionMode getProtectionMode()
• void setProtectionMode(ProtectionMode pmode)

Read/write methods:

• void enableWrite(): does not need to be called explicitly before write operation, but saves a few cpu cycles
• void disableWrite()
• bool readBytes(uint8_t *dst, addr_t address, addr_t n)
• bool writeBytes(addr_t address, uint8_t *src, addr_t n)

Power saving:

• void sleep()
• void wake()
• bool isSleeping(): every command sent while sleeping will be ignored

Helper functions:

• void eraseChip(uint8_t value = 0xff)
• void eraseFullChip(uint8_t value = 0xff)