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Figure 2. Oscillator Connections
Note:
When using the MCU Oscillator as a clock for an external device, an HC buffer should be connected as indicated in the figure.
Figure 3. External Clock Drive Configuration
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.
The ALU supports arithmetic and logic functions between registers or between a constant and a register. Single register
operations are also executed in the ALU. Figure 4 shows the AT90S4414/8515 AVR RISC microcontroller architecture.
In addition to the register operation, the conventional memory 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,
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.
MAX 1 HC BUFFER
HC
C2
XTAL2
C1
XTAL1
GND
AT90S4414/8515
5
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