Bitwise operations and masks: basics, help?

[falingtrea]

What I would do is:

PORTC = PORTC & %11100000   / Clear all the bits in PORTC that are segments
PORTC = AVAL[x] | PORTC        / sets the bits in PORTC that are '1' in AVAL[x]

PORTA = PORTA & %11111001  /  Clear all the bits in PORTA that are segments
PORTA = CVAL[x] | PORTA       / sets the bits in PORTA that are '1' in CVAL[x]

if you just want to use one matrix for segment data you can do this:

ORMASK = SEGVAL[x] & %00011111 / makes sure only 5 lsb of SEGVAL[x] '1' bits get set below
PORTC = PORTC & %11100000    / Clear all the bits in PORTC that are segments 
PORTC = ORMASK | PORTC         / sets the bits in PORTC that are '1' in AVAL[x]

ORMASK = SEGVAL[x] >> 4         / shift data 4 to right to position correct SEGVAL[x] bits for PORTA
ORMASK = ORMASK & %0000110 / makes sure only 2 bits of SEGVAL[x] '1' bits get set below
PORTA = PORTA | %11111001    / Clear all the bits in PORTA that are segments
PORTA = ORMASK | PORTA        / sets the bits in PORTC that are '1' in AVAL[x]