how to calculate the number of address lines ?

[ushisna]

how many address lines ?

I got one doubt regarding bus interface .
A peripheral of 512 Mbits has 16 bit data bus width.
I need to calculate the total number of address lines of the peripheral.


If it is 512 Mbyte and 16 bit databus width then ,as per my understanding the total number of address lines required will be 25 lines

512 Mbytes = (2^20) x 2^ 9 = 2^ 29
The data bus is 16 bits so Address bus will be ( 2^29) / (2x2^3) = 2 ^ 25
So total of 25 lines ..



But if the capacity is 512 Mbits ,I got confused on how many number of address lines will be required ?


Could anyone please help me to get it clarified?

Many Thanks
Usha

 

[GrandAlf]

how many address lines ?

I make it 29 lines for 536Mbit. If you are not sure, you can just keep doubling up 1-2-4-8-16 etc, until you get to the number in Mbits that you need. Just keep count of the number of times you have doubled to get the address lines needed. 16 address lines would give 64kbits (65536) if I remember correctly.

So follow on from this:
17 131072
18 262144
19 524288
20 1048576
21 2097152
22 4194304
23 8388608
24 16777216
25 33554432
26 67108864
27 134217728
28 268435456
29 536870912 This one needed 536 Mbits

 

[laktronics]

Re: how many address lines ?

Hi,
Yes, you are right, with 25 address lines you can address 32M words, each of 16bit width. So you can handle up to 512Mbits using a system having 25 address lines and 16bit data width.
Hi, GrandAlf, in the binary world, 1K is 1024 and not 1000 as in decimal system.

Regards,
Laktronics

 

[GrandAlf]

how many address lines ?

Of course I hardly need to mention that its just 2^x anyway. Just trying to show how it builds up.

Added after 24 minutes:

I missed the fact it was 16 bit...Doh! Sorry for the confusion. Don't really understand the relevance to decimal, we all know what 1k etc is.