AT90S4414 Architectural Overview
The fast-access register file concept contains 32 x 8-bit
general purpose working registers with a single clock cycle
access time. This means that during one single clock cycle,
one ALU (Arithmetic Logic Unit) operation is executed. Two
operands are output from the register file, the operation is
executed, and the result is stored back in the register file -
in one clock cycle. Six of the 32 registers can be used as
three 16-bits indirect address register pointers for Data
Space addressing - enabling efficient address calculations.
One of the three address pointers is also used as the
address pointer for the constant table look up function.
These added function registers are the 16-bits X-register,
Y-register and Z-register.
Figure 4. The AT90S4414 AVR Enhanced RISC Architecture
The ALU supports arithmetic and logic functions between
registers or between a constant and a register. Single reg-
ister operations are also executed in the ALU. Figure 4
shows the AT90S4414 AVR Enhanced RISC microcontrol-
ler architecture.
A/D-converters, and other I/O functions. The I/O Memory
can be accessed directly, or as the Data Space locations
following those of the register file, $20 - $5F.
The AVR uses a Harvard architecture concept - with sepa-
rate memories and buses for program and data. The pro-
gram memory is executed with a two stage pipeline. While
one instruction is being executed, the next instruction is
pre-fetched from the program memory. This concept
enables instructions to be executed in every clock cycle.
The program memory is in-system In-System Programma-
ble Flash memory.
In addition to the register operation, the conventional mem-
ory addressing modes can be used on the register file as
well. This is enabled by the fact that the register file is
assigned the 32 lowermost Data Space addresses ($00 -
$1F), allowing them to be accessed as though they were
ordinary memory locations.
The I/O memory space contains 64 addresses for CPU
peripheral functions as Control Registers, Timer/Counters,
With the relative jump and call instructions, the whole 2K
address space is directly accessed. Most AVR instructions
AT90S4414
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ATMEL [ ATMEL ]
