Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Scheda Tecnica

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SAM4E [DATASHEET]

Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14

 

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).

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.