
21
2543L–AVR–08/10
ATtiny2313
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.
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, unlike most other
AVRs, the CBI and SBI instructions will only operate on the specified bit, and can therefore be
used on registers containing such status flags. The CBI and SBI instructions work with registers
0x00 to 0x1F only.
The I/O and peripherals control registers are explained in later sections.
General Purpose I/O
Registers
The ATtiny2313 contains three General Purpose I/O Registers. These registers can be used for
storing any information, and they are particularly useful for storing global variables and status
flags. General Purpose I/O Registers within the address range 0x00 - 0x1F are directly bit-
accessible using the SBI, CBI, SBIS, and SBIC instructions.
General Purpose I/O
Register 2 – GPIOR2
General Purpose I/O
Register 1 – GPIOR1
General Purpose I/O
Register 0 – GPIOR0
Bit
765
4321
0
MSB
LSB
GPIOR2
Read/Write
R/W
Initial Value
000
0000
0
Bit
765
4321
0
MSB
LSB
GPIOR1
Read/Write
R/W
Initial Value
000
0000
0
Bit
765
4321
0
MSB
LSB
GPIOR0
Read/Write
R/W
Initial Value
000
0000
0