Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Fiche De Données
Codes de produits
ATSAM4S-WPIR-RD
73
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
Accesses to the 32 MB SRAM alias region map to the 1 MB SRAM bit-band region, as shown in
Accesses to the 32 MB peripheral alias region map to the 1 MB peripheral bit-band region, as shown in
.
Notes: 1. A word access to the SRAM or peripheral bit-band alias regions map to a single bit in the SRAM or peripheral bit-band
region.
2. Bit-band accesses can use byte, halfword, or word transfers. The bit-band transfer size matches the transfer size of the
instruction making the bit-band access.
The following formula shows how the alias region maps onto the bit-band region:
bit_word_offset = (byte_offset x 32) + (bit_number x 4)
bit_word_addr = bit_band_base + bit_word_offset
where:
Bit_word_offset
is the position of the target bit in the bit-band memory region.
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.
shows examples of bit-band mapping between the SRAM bit-band alias region and the SRAM bit-
band region:
The alias word at 0x23FFFFE0 maps to bit[0] of the bit-band byte at 0x200FFFFF: 0x23FFFFE0 =
0x22000000 + (0xFFFFF*32) + (0*4).
The alias word at 0x23FFFFFC maps to bit[7] of the bit-band byte at 0x200FFFFF: 0x23FFFFFC =
0x22000000 + (0xFFFFF*32) + (7*4).
The alias word at 0x22000000 maps to bit[0] of the bit-band byte at 0x20000000: 0x22000000 =
0x22000000 + (0*32) + (0*4).
The alias word at 0x2200001C maps to bit[7] of the bit-band byte at 0x20000000: 0x2200001C =
0x22000000+ (0*32) + (7*4).
Table 12-6.
SRAM Memory Bit-banding Regions
Address Range
Memory Region
Instruction and Data Accesses
0x20000000–0x200FFFFF
SRAM bit-band region
Direct accesses to this memory range behave as SRAM memory accesses,
but this region is also bit-addressable through bit-band alias.
0x22000000–0x23FFFFFF
SRAM bit-band alias
Data accesses to this region are remapped to bit-band region. A write
operation is performed as read-modify-write. Instruction accesses are not
remapped.
Table 12-7.
Peripheral Memory Bit-banding Regions
Address Range
Memory Region
Instruction and Data Accesses
0x40000000–0x400FFFFF
Peripheral bit-band alias
Direct accesses to this memory range behave as peripheral memory
accesses, but this region is also bit-addressable through bit-band alias.
0x42000000–0x43FFFFFF
Peripheral bit-band region
Data accesses to this region are remapped to bit-band region. A write
operation is performed as read-modify-write. Instruction accesses are not
permitted.