Rainbow Electronics ATmega162V - Manual (Page 23)

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ATmega162/V
2513E–AVR–09/03
Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
This can be done by enabling the internal Brown-out Detector (BOD). If the detection
level of the internal BOD does not match the needed detection level, an external low
V
CC
Reset Protection circuit can be used. If a Reset occurs while a write operation is in
progress, the write operation will be completed provided that the power supply voltage is
sufficient.
I/O Memory The I/O space definition of the ATmega162 is shown in “Register Summary” on page
303.
All ATmega162 I/Os and peripherals are placed in the I/O space. All I/O locations may
be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data
between the 32 general purpose working registers and the I/O space. I/O Registers
within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI
instructions. In these registers, the value of single bits can be checked by using the
SBIS and SBIC instructions. Refer to the instruction set section for more details. When
using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be
used. When addressing I/O Registers as data space using LD and ST instructions, 0x20
must be added to these addresses. The ATmega162 is a complex microcontroller with
more peripheral units than can be supported within the 64 location reserved in Opcode
for the IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in SRAM,
only the ST/STS/STD and LD/LDS/LDD instructions can be used. The Extended I/O
space is replaced with SRAM locations when the ATmega162 is in the ATmega161
compatibility mode.
For compatibility with future devices, reserved bits should be written to zero if accessed.
Reserved I/O memory addresses should never be written.
Some of the Status Flags are cleared by writing a logical one to them. Note that the CBI
and SBI instructions will operate on all bits in the I/O Register, writing a one back into
any flag read as set, thus clearing the flag. The CBI and SBI instructions work with reg-
isters 0x00 to 0x1F only.
The I/O and peripherals control registers are explained in later sections.