Datasheet

2549O–AVR–05/12

ATmega640/1280/1281/2560/2561

7.6.1 RAMPZ – Extended Z-pointer Register for ELPM/SPM

For ELPM/SPM instructions, the Z-pointer is a concatenation of RAMPZ, ZH, and ZL, as shown

in Figure 7-4. Note that LPM is not affected by the RAMPZ setting.

Figure 7-4. The Z-pointer used by ELPM and SPM

The actual number of bits is implementation dependent. Unused bits in an implementation will

always read as zero. For compatibility with future devices, be sure to write these bits to zero.

7.6.2 EIND – Extended Indirect Register

For EICALL/EIJMP instructions, the Indirect-pointer to the subroutine/routine is a concatenation

of EIND, ZH, and ZL, as shown in Figure 7-5. Note that ICALL and IJMP are not affected by the

EIND setting.

Figure 7-5. The Indirect-pointer used by EICALL and EIJMP

The actual number of bits is implementation dependent. Unused bits in an implementation will

always read as zero. For compatibility with future devices, be sure to write these bits to zero.

7.7 Instruction Execution Timing

This section describes the general access timing concepts for instruction execution. The AVR

CPU is driven by the CPU clock clk

CPU

, directly generated from the selected clock source for the

chip. No internal clock division is used.

Figure 7-6 on page 18 shows the parallel instruction fetches and instruction executions enabled

by the Harvard architecture and the fast-access Register File concept. This is the basic pipelin-

ing concept to obtain up to 1 MIPS per MHz with the corresponding unique results for functions

per cost, functions per clocks, and functions per power-unit.

Bit 765432 1 0

0x3B (0x5B)

RAMPZ7 RAMPZ6 RAMPZ5 RAMPZ4 RAMPZ3 RAMPZ2 RAMPZ1 RAMPZ0

RAMPZ

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value000000 0 0

Bit (

Individually)

707070

RAMPZ ZH ZL

Bit (Z-pointer) 23 16 15 8 7 0

Bit 765432 1 0

0x3C (0x5C) EIND7 EIND6 EIND5 EIND4 EIND3 EIND2 EIND1 EIND0 EIND

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value000000 0 0

Bit (Individual-

ly)

707070

EIND ZH ZL

Bit (Indirect-

pointer)

23 16 15 8 7 0