26
7734Q–AVR–02/12
AT90PWM81/161
4.5
I/O Memory
All AT90PWM81/161 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
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
AT90PWM81/161 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.
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
AVR’s, 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.
4.6
General Purpose I/O Registers
The AT90PWM81/161 contains four 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.
The General Purpose I/O Registers, within the address range 0x00 - 0x1F, are directly bit-
accessible using the SBI, CBI, SBIS, and SBIC instructions.
4.6.1
GPIOR0 - General Purpose I/O Register 0
4.6.2
GPIOR1 - General Purpose I/O Register 1
4.6.3
GPIOR2 - General Purpose I/O Register 2
Bit
76543210
GPIOR07
GPIOR06
GPIOR05
GPIOR04
GPIOR03
GPIOR02
GPIOR01
GPIOR00
GPIOR0
Read/Write
R/W
Initial Value
00000000
Bit
76543210
GPIOR17
GPIOR16
GPIOR15
GPIOR14
GPIOR13
GPIOR12
GPIOR11
GPIOR10
GPIOR1
Read/Write
R/W
Initial Value
00000000
Bit
76543210
GPIOR27
GPIOR26
GPIOR25
GPIOR24
GPIOR23
GPIOR22
GPIOR21
GPIOR20
GPIOR2
Read/Write
R/W
Initial Value
00000000