23
XMEGA B [DATASHEET]
8291B–AVR–01/2013
Figure 4-2.
Data memory map.
I/O memory, EEPROM, and SRAM will always have the same start addresses for all XMEGA devices.
4.6
Internal SRAM
The internal SRAM always starts at hexadecimal address 0x2000. SRAM is accessed by the CPU using the load
(LD/LDS/LDD) and store (ST/STS/STD) instructions.
4.7
EEPROM
XMEGA devices have EEPROM for nonvolatile data storage. It is either addressable in a separate data space (default)
or memory mapped and accessed in normal data space. The EEPROM supports both byte and page access. Memory
mapped EEPROM allows highly efficient EEPROM reading and EEPROM buffer loading. When doing this, EEPROM is
accessible using load and store instructions. Memory mapped EEPROM will always start at hexadecimal address
0x1000.
4.8
I/O Memory
The status and configuration registers for peripherals and modules, including the CPU, are addressable through I/O
memory locations. All I/O locations can be accessed by the load (LD/LDS/LDD) and store (ST/STS/STD) instructions,
which are used to transfer data between the 32 registers in the register file and the I/O memory. The IN and OUT
instructions can address I/O memory locations in the range of 0x00 to 0x3F directly. In the address range 0x00 - 0x1F,
single-cycle instructions for manipulation and checking of individual bits are available.
4.8.1
General Purpose I/O Registers
The lowest 4 I/O memory addresses are reserved as general purpose I/O registers. These registers can be used for
storing global variables and flags, as they are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.
4.9
Data Memory and Bus Arbitration
Since the data memory is organized as four separate sets of memories, the different bus masters (CPU, DMA controller
read and DMA controller write, etc.) can access different memories at the same time. As
shows,
I/O Memory
(Up to 4 KB)
EEPROM
(Up to 4 KB)
Internal SRAM
(Up to 8 KB)
0x0000
0x1000
0x2000
Start/End Address
Data Memory
Содержание XMEGA B
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