Rainbow Electronics ATtiny12 - Manual (Page 14)

14
ATtiny11/12
1006C–09/01
I/O Memory The I/O space definition of the ATtiny11/12 is shown in the following table:
Note: Reserved and unused locations are not shown in the table.
All the different ATtiny11/12 I/O and peripherals are placed in the I/O space. The differ-
ent I/O locations are accessed by the IN and OUT instructions transferring data between
the 32 general-purpose working registers and the I/O space. I/O registers within the
address range $00 - $1F 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 Summary for more details.
For compatibility with future devices, reserved bits should be written to zero if accessed.
Reserved I/O memory addressed should never be written.
The different I/O and peripherals control registers are explained in the following
sections.
Status Register – SREG The AVR status register (SREG) at I/O space location $3F is defined as:
• Bit 7 - I: Global Interrupt Enable
The global interrupt enable bit must be set (one) for the interrupts to be enabled. The
individual interrupt enable control is then performed in separate control registers. If the
global interrupt enable register is cleared (zero), none of the interrupts are enabled inde-
Table 4. ATtiny11/12 I/O Space
Address Hex Name Device Function
$3F SREG ATtiny11/12 Status Register
$3B GIMSK ATtiny11/12 General Interrupt Mask Register
$3A GIFR ATtiny11/12 General Interrupt Flag Register
$39 TIMSK ATtiny11/12 Timer/Counter Interrupt Mask Register
$38 TIFR ATtiny11/12 Timer/Counter Interrupt Flag Register
$35 MCUCR ATtiny11/12 MCU Control Register
$34 MCUSR ATtiny11/12 MCU Status Register
$33 TCCR0 ATtiny11/12 Timer/Counter0 Control Register
$32 TCNT0 ATtiny11/12 Timer/Counter0 (8-bit)
$31 OSCCAL ATtiny12 Oscillator Calibration Register
$21 WDTCR ATtiny11/12 Watchdog Timer Control Register
$1E EEAR ATtiny12 EEPROM Address Register
$1D EEDR ATtiny12 EEPROM Data Register
$1C EECR ATtiny12 EEPROM Control Register
$18 PORTB ATtiny11/12 Data Register, Port B
$17 DDRB ATtiny11/12 Data Direction Register, Port B
$16 PINB ATtiny11/12 Input Pins, Port B
$08 ACSR ATtiny11/12 Analog Comparator Control and Status Register
Bit 7 6 5 4 3 2 1 0
$3F I T H S V N Z C SREG
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0