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ATmega16M1/32M1/64M1 [DATASHEET]
8209E–AVR–11/2012
The ATmega16M1/32M1/64M1 is a complex microcontroller with more peripheral units than can be supported
within the 64 locations reserved in the Opcode for the IN and OUT instructions. For the Extended I/O space from
0x60 - 0xFF in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can be used.
The lower 2304 data memory locations address both the Register File, the I/O memory, Extended I/O memory, and
the internal data SRAM. The first 32 locations address the Register File, the next 64 location the standard I/O
memory, then 160 locations of Extended I/O memory, and the next 1/2/4K locations address the internal data
SRAM.
The five different addressing modes for the data memory cover: Direct, Indirect with Displacement, Indirect, Indi-
rect with Pre-decrement, and Indirect with Post-increment. In the Register File, registers R26 to R31 feature the
indirect addressing pointer registers.
The direct addressing reaches the entire data space.
The Indirect with Displacement mode reaches 63 address locations from the base address given by the Y-register
or Z-register.
When using register indirect addressing modes with automatic pre-decrement and post-increment, the address
registers X, Y, and Z are decremented or incremented.
The 32 general purpose working registers, 64 I/O Registers, 160 Extended I/O Registers, and the 1/2/4K bytes of
internal data SRAM in the ATmega16M1/32M1/64M1 are all accessible through all these addressing modes. The
Figure 7-2.
Data memory map1/2/4K.
7.3.1
SRAM data access times
This section describes the general access timing concepts for internal memory access. The internal data SRAM
access is performed in two clk
32 registers
64 I/O registers
Internal SRAM
(1024/2048/4096 x 8)
0x0000 - 0x001F
0x0020 - 0x005F
0x04FF/0x08FF/0x10FF
0x0060 - 0x00FF
Data memory
160 ext I/O reg.
0x0100