I/o memory – Rainbow Electronics AT90C8534 User Manual

Page 16

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AT90C8534

I/O Memory

The I/O space definition of the AT90C8534 is shown in Table 1.

Note:

Reserved and unused locations are not shown in the table.

The AT90C8534 I/Os and peripherals are placed in the I/O space. The 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 section for more details.
When using the I/O specific commands, IN and OUT, the I/O addresses $00 - $3F must be used. When addressing I/O reg-
isters 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.

The I/O and peripherals control registers are explained in the following sections.

Table 1. AT90C8534 I/O Space

I/O Address (SRAM Address)

Name

Function

$3F ($5F)

SREG

Status REGister

$3E ($5E)

SPH

Stack Pointer High

$3D ($5D)

SPL

Stack Pointer Low

$3B ($5B)

GIMSK

General Interrupt MaSK register

$3A ($5A)

GIFR

General Interrupt Flag Register

$39 ($59)

TIMSK

Timer/Counter Interrupt MaSK register

$38 ($58)

TIFR

Timer/Counter Interrupt Flag register

$35 ($55)

MCUCR

MCU general Control Register

$33 ($53)

TCCR0

Timer/Counter0 Control Register

$32 ($52)

TCNT0

Timer/Counter0 (8-bit)

$2E ($4E)

TCCR1

Timer/Counter1 Control Register

$2D ($4D)

TCNT1H

Timer/Counter1 High Byte

$2C ($4C)

TCNT1L

Timer/Counter1 Low Byte

$1F ($3E)

EEARH

EEPROM Address Register High Byte

$1E ($3E)

EEARL

EEPROM Address Register Low Byte

$1D ($3D)

EEDR

EEPROM Data Register

$1C ($3C)

EECR

EEPROM Control Register

$1B ($3B)

PORTA

Data Register, Port A

$1A ($3A)

DDRA

Data Direction Register, Port A

$10 ($30)

GIPR

General Interrupt Pin 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

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