Rainbow Electronics AT90S1200 - Manual (Page 10)

10
AT90S1200
0838H–AVR–03/02
I/O Memory The I/O space definition of the AT90S1200 is shown in the following table.
Note: Reserved and unused locations are not shown in the table.
All AT90S1200 I/Os and peripherals are placed in the I/O space. The different I/O loca-
tions 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 instruc-
tions. Refer to the instruction set chapter for more details.
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.
The different I/O and peripherals control registers are explained in the following
sections.
Table 1. The AT90S1200 I/O Space
Address Hex Name Function
$3F SREG Status REGister
$3B GIMSK General Interrupt MaSK register
$39 TIMSK Timer/Counter Interrupt MaSK register
$38 TIFR Timer/Counter Interrupt Flag register
$35 MCUCR MCU general Control Register
$33 TCCR0 Timer/Counter0 Control Register
$32 TCNT0 Timer/Counter0 (8-bit)
$21 WDTCR Watchdog Timer Control Register
$1E EEAR EEPROM Address Register
$1D EEDR EEPROM Data Register
$1C EECR EEPROM Control Register
$18 PORTB Data Register, Port B
$17 DDRB Data Direction Register, Port B
$16 PINB Input Pins, Port B
$12 PORTD Data Register, Port D
$11 DDRD Data Direction Register, Port D
$10 PIND Input Pins, Port D
$08 ACSR Analog Comparator Control and Status Register