AT90CAN64 datasheet(13/431 Pages) ATMEL

13 / 431 page

7682C–AUTO–04/08

AT90CAN32/64/128

Figure 3-3.

The X-, Y-, and Z-registers

In the different addressing modes these address registers have functions as fixed displacement,

automatic increment, and automatic decrement (see the instruction set reference for details).

3.5.2

Extended Z-pointer Register for ELPM/SPM – RAMPZ

• Bits 7..1 – Res: Reserved Bits

These bits are reserved for future use and will always read as zero. For compatibility with future

devices, be sure to write to write them to zero.

• Bit 0 – RAMPZ0: Extended RAM Page Z-pointer

The RAMPZ Register is normally used to select which 64K RAM Page is accessed by the Z-

pointer. As the AT90CAN32/64/128 does not support more than 64K of SRAM memory, this reg-

ister is used only to select which page in the program memory is accessed when the ELPM/SPM

instruction is used. The different settings of the RAMPZ0 bit have the following effects:

– AT90CAN32 and AT90CAN64: RAMPZ0 exists as register bit but it is not used for

program memory addressing.

– AT90CAN128: RAMPZ0 exists as register bit and it is used for program memory

addressing.

Figure 3-4.

The Z-pointer used by ELPM and SPM

Note:

LPM (different of ELPM) is never affected by the RAMPZ setting.

X-register

R27 (0x1B)

R26 (0x1A)

Y-register

R29 (0x1D)

R28 (0x1C)

Z-register

R31 (0x1F)

R30 (0x1E)

Bit

–

RAMPZ0

RAMPZ

Read/Write

R/W

Initial Value

RAMPZ0 = 0: Program memory address 0x0000 - 0x7FFF (lower 64K bytes) is accessed by

ELPM/SPM

RAMPZ0 = 1: Program memory address 0x8000 - 0xFFFF (higher 64K bytes) is accessed by

ELPM/SPM

RAMPZ

Bit (Individually)

Bit (Z-pointer)

AT90CAN64 Datasheet(PDF) 13 Page - ATMEL Corporation

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