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8127C–AVR–10/09

ATtiny4/5/9/10

5.3

I/O Memory

The I/O space definition of the ATtiny4/5/9/10 is shown in “Register Summary” on page 149.

All ATtiny4/5/9/10 I/Os and peripherals are placed in the I/O space. All I/O locations may be

accessed using the LD and ST instructions, enabling data transfer between the 16 general pur-

pose 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 sin-

gle bits can be checked by using the SBIS and SBIC instructions. See document “AVR

Instruction Set” and section “Instruction Set Summary” on page 151 for more details. When

using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must 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 CBI and SBI

instructions will only operate on the specified bit, and can therefore be used on registers contain-

ing such status flags. The CBI and SBI instructions work on registers in the address range 0x00

to 0x1F, only.

The I/O and Peripherals Control Registers are explained in later sections.

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