i/o address explanation

jony265

i am having somewhat of a hard time w/ i/o addressing and the memorization involved. i was wondering if someone could plz explain how they came upon this number-letter combo? i understand hexadecimal and i have the irq down pretty well but i need to know why they are labeled this way. btw i am taking the core on laborday and i already passed the os part but it wasn't by much...lol...i made it to question 30 if that means anything, but my book is a pathetic resource...thx

jrowe

every device in the pc has an address so the cpu can talk to it.
that address is 16 binary digits long
now if you understand hex you can see that 16 binary digits break down into 4 lots of 4
i.e. 1111 1111 1111 1111
4 binary digits being equal to 1 hex value
i.e. binary 0000=hex 0
0001=hex 1
1010=hex A
etc. etc. covering the 16 possible combinations

all devices use more than one address, so a range is specified
i.e. com 1 = 03F8-03FF
to write that down in binary would be 32 digits long

jony265

what i don't understand is how it goes from 1010=hex A
what is the formula for that?

btw...thx for quick reply

jrowe

binary - base 2 numbering system
decimal - base 10 numbering system (the way we count)
hexadecimal - base 16 numbering system

binary - hex
0000 = 0
0001 = 1
0010 = 2
0011 = 3
0100 = 4
0101 = 5
0110 = 6
0111 = 7
1000 = 8
1001 = 9
1010 = A
1011 = B
1100 = C
1101 = D
1110 = E
1111 = F

jony265

ok WOW thank-you sooo much...now i can reason and understand this labeling system it won't be hard to remember(no need to memorize) thx alot