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8210C–AVR–09/11
Atmel AVR XMEGA D
4.8.1
General Purpose I/O Registers
The lowest 4 I/O memory addresses are reserved as general purpose I/O registers. These regis-
ters can be used for storing global variables and flags, as they are directly bit-accessible using
the SBI, CBI, SBIS, and SBIC instructions.
Figure 4-3.
Bus access.
4.9
Memory Timing
Read and write access to the I/O memory takes one CPU clock cycle. A write to SRAM takes
one cycle, and read from SRAM takes two cycles. Refer to the instruction summary for more
details on instructions and instruction timing.
4.10
Device ID and Revision
Each device has a three-byte device ID. This ID identifies Atmel as the manufacturer of the
device and the device type. A separate register contains the revision number of the device.
4.11
I/O Memory Protection
Some features in the device are regarded as critical for safety in some applications. Due to this,
it is possible to lock the I/O register related to the clock system, the event system and the
advanced waveform extensions. As long as the lock is enabled, all related I/O registers are
locked and they can not be written from the application software. The lock registers themselves
are protected by the configuration change protection mechanism. For details refer to
tion Change Protection” on page 11
.
Peripherals and system modules
Bus matrix
CPU
RAM
OCD
USART
SPI
Timer /
Counter
TWI
Interrupt
Controller
Power
Management
SRAM
External
Programming
PDI
AVR core
ADC
AC
Event System
Controller
Oscillator
Control
Non-Volatile
Memory
EEPROM
Flash
CRC
Real Time
Counter
I/O
NVM
Controller