AT90S4414/8515
15
Indirect Program Addressing, IJMP and ICALL
Figure 18. Indirect Program Memory Addressing
Program execution continues at address contained by the Z-register (i.e. the PC is loaded with the contents of the
Z-register).
Relative Program Addressing, RJMP and RCALL
Figure 19. Relative Program Memory Addressing
Program execution continues at address PC + k + 1. The relative address k is -2048 to 2047.
EEPROM Data Memory
The AT90S4414/8515 contains 256/512 bytes of data EEPROM memory. It is organized as a separate data space, in
which single bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. The
access between the EEPROM and the CPU is described on page 39 specifying the EEPROM address registers, the
EEPROM data register, and the EEPROM control register.
For the SPI data downloading, see page 77 for a detailed description.
Memory Access Times and Instruction Execution Timing
This section describes the general access timing concepts for instruction execution and internal memory access.
The AVR CPU is driven by the System Clock Ø, directly generated from the external clock crystal for the chip. No internal
clock division is used.
Figure 20 shows the parallel instruction fetches and instruction executions enabled by the Harvard architecture and the
fast-access register file concept. This is the basic pipelining 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.
$000
$7FF/$FFF
PROGRAM MEMORY
15
0
Z-REGISTER
$000
$7FF/$FFF
PROGRAM MEMORY
15
0
15
0
12 11
PC
OP
k