7.10 I/O Memory

All ATtiny3224/3226/3227 devices’ I/O and peripheral registers are located in the I/O memory space. Refer to the Peripheral Address Map table for further details.

For compatibility with a future device, if a register containing reserved bits is written, the reserved bits should be written to ‘0’. Reserved I/O memory addresses should never be written.

Single-Cycle I/O Registers

The I/O memory ranging from 0x00 to 0x3F can be accessed by a single-cycle CPU instruction using the IN or OUT instructions.

The peripherals available in the single-cycle I/O registers are as follows:

  • VPORTx
    • Refer to the I/O Configuration section for further details
  • GPIO
    • Refer to the I/O Configuration section for further details
  • CPU
    • Refer to the AVR CPU section for further details

The single-cycle I/O registers ranging from 0x00 to 0x1F (VPORTx and GPIO) are also directly bit-accessible using the SBI or CBI instruction. In these single-cycle I/O registers, single bits can be checked by using the SBIS or SBIC instruction.

Refer to the Instruction Set Summary for further details.