Rainbow-electronics ATmega128L Manuel d'utilisateur télécharger pdf (Page 18)

ATmega128(L)

2467B–09/01

The five different addressing modes for the data memory cover: Direct, Indirect with Dis-

placement, Indirect, Indirect 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- 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, and the 4096 bytes of inter-

nal data SRAM in the ATmega128 are all accessible through all these addressing

modes. The Register file is described in

“General Purpose Register File” on page 10.

Figure 9. Data Memory Map

Data Memory Access Times This section describes the general access timing concepts for internal memory access.

The internal data SRAM access is performed in two clk

CPU

cycles as described in Figure

Memory Configuration B

32 Registers

64 I/O Registers

Internal SRAM

(4000 x 8)

$0000 - $001F

$0020 - $005F

$1000

$0FFF

$FFFF

$0060

Data Memory

External SRAM

(0 - 64K x 8)

Memory Configuration A

32 Registers

64 I/O Registers

Internal SRAM

(4096 x 8)

$0000 - $001F

$0020 - $005F

$1100

$10FF

$FFFF

$0060 - $00FF

Data Memory

External SRAM

(0 - 64K x 8)

160 Ext I/O Reg.

$0100

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 330 331

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Rainbow-electronics ATmega128L Manuel d'utilisateur Page 18

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