Rainbow Electronics ATmega103L User Manual

Page 20

ATmega603/103

Note:

Reserved and unused locations are not shown in the table

All the different ATmega603/103 I/Os and peripherals are placed in the I/O space. The different I/O locations are directly
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 chapter for more details. When using the I/O specific instructions IN, OUT, the I/O register address $00 - $3F are used.
When addressing I/O registers as SRAM, $20 must be added to this address. All I/O register addresses throughout this
document are shown with the SRAM address in parentheses.

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 the CBI and SBI instructions will operate on
all bits in the I/O register, writing a one back into any flag read as set, thus clearing the flag. The CBI and SBI instructions
work with registers $00 to $1F only.

$1B ($3B)

PORTA

Data Register, Port A

$1A ($3A)

DDRA

Data Direction Register, Port A

$19 ($39)

PINA

Input Pins, Port A

$18 ($38)

PORTB

Data Register, Port B

$17 ($37)

DDRB

Data Direction Register, Port B

$16 ($36)

PINB

Input Pins, Port B

$15 ($35)

PORTC

Data Register, Port C

$12 ($32)

PORTD

Data Register, Port D

$11 ($31)

DDRD

Data Direction Register, Port D

$10 ($30)

PIND

Input Pins, Port D

$0F ($2F)

SPDR

SPI I/O Data Register

$0E ($2E)

SPSR

SPI Status Register

$0D ($2D)

SPCR

SPI Control Register

$0C ($2C)

UDR

UART I/O Data Register

$0B ($2B)

USR

UART Status Register

$0A ($2A)

UCR

UART Control Register

$09 ($29)

UBRR

UART Baud Rate Register

$08 ($28)

ACSR

Analog Comparator Control and Status Register

$07 ($27)

ADMUX

ADC Multiplexer Select Register

$06 ($26)

ADCSR

ADC Control and Status Register

$05 ($25)

ADCH

ADC Data Register High

$04 ($24)

ADCL

ADC Data Register Low

$03 ($23)

PORTE

Data Register, Port E

$02 ($22)

DDRE

Data Direction Register, Port E

$01 ($21)

PINE

Input Pins, Port E

$00 ($20)

PINF

Input Pins, Port F

Table 3. ATmega603/103 I/O Space (Continued)

I/O Address (SRAM Address)

Name

Function