TWBR|TWSR|TWAR|TWDR|ADCL|ADCH|ADCSRA|ADMUX|ACSR|UBRRL|UCSRB|
UCSRA|UDR|SPCR|SPSR|SPDR|PIND|DDRD|PORTD|PINC|DDRC|PORTC|
PINB|DDRB|PORTB|PINA|DDRA|PORTA|EECR|EEDR|EEARL|EEARH|UBRRH|
WDTCR|ASSR|OCR2|TCNT2|TCCR2|ICR1L|ICR1H|OCR1BL|OCR1BH|OCR1AL|
OCR1AH|TCNT1L|TCNT1H|TCCR1B|TCCR1A|SFIOR|OSCCAL|TCNT0|TCCR0|MCUCSR|
MCUCR|TWCR|SPMCR|TIFR|TIMSK|GIFR|GICR|OCR0|SPL|SPH|SREG|

ATmega8535 I/O registers 0..3F description
