Embedded Sram - ST STM32L4x6 Reference Manual

alias region has the same effect as a read-modify-write operation on the targeted bit in the
bit-band region.
In the STM32L4x6 devices both the peripheral registers and the SRAM1 are mapped to a
bit-band region, so that single bit-band write and read operations are allowed. The
operations are only available for Cortex
(e.g. DMA).
A mapping formula shows how to reference each word in the alias region to a corresponding
bit in the bit-band region. The mapping formula is:
bit_word_addr = bit_band_base + (byte_offset x 32) + (bit_number × 4)
where:
–
–
–
–
Example
The following example shows how to map bit 2 of the byte located at SRAM1 address
0x20000300 to the alias region:
0x22006008 = 0x22000000 + (0x300*32) + (2*4)
Writing to address 0x22006008 has the same effect as a read-modify-write operation on bit
2 of the byte at SRAM1 address 0x20000300.
Reading address 0x22006008 returns the value (0x01 or 0x00) of bit 2 of the byte at SRAM1
address 0x20000300 (0x01: bit set; 0x00: bit reset).
For more information on bit-banding, please refer to the Cortex
(see Related documents on page
2.4

Embedded SRAM

The STM32L4x6 devices feature up to 128 Kbyte SRAM:
• Up to 96 Kbyte SRAM1.
• 32 Kbyte SRAM2.
These SRAM can be accessed as bytes, half-words (16 bits) or full words (32 bits). These
memories can be addressed at maximum system clock frequency without wait state and
thus by both CPU and DMA.
The CPU can access the SRAM1 through the System bus or through the ICode/DCode
buses when boot from SRAM1 is selected or when physical remap is selected
(Section 8.2.1: SYSCFG memory remap register (SYSCFG_MEMRMP)
controller). To get the maximum performance on SRAM1 execution, physical remap should
be selected (boot or software selection).
Execution can be performed from SRAM2 with maximum performance without any remap
thanks to access through ICode bus.
72/1693
bit_word_addr is the address of the word in the alias memory region that maps to
the targeted bit
bit_band_base is the starting address of the alias region
byte_offset is the number of the byte in the bit-band region that contains the
targeted bit
bit_number is the bit position (0-7) of the targeted bit
DocID024597 Rev 3
®
-M4 accesses, and not from other bus masters
1).
RM0351
®
-M4 programming manual
in the SYSCFG