NCEES FE Electrical and Computer Practice Question Help

[wbishop256]

It seems I put my question in the wrong section, so I'm reposting it here:

Hello!

Here's a question from the Pratice Exam I'd like some help on:



The correct answer is C. I understand that only CS4 and A15-13 matter for the answer... I just don't understand how. Could someone please walk me through this problem? Explain it to me like I'm idiot?

Thanks.

 

[xnuke]

List out the address range spaces 15 to 0, then start putting a 1 or 0 as needed for each space. For CS4 to go low, A15 = 1, A14 = 0, A13 = 0, so those are defined as such. This leaves A12 to A0 as don't care bits. When coupled with 1 0 0 for bits 15-12, if A12 through A0 are all 0 to find the bottom end of the range, you get 1000/0000/0000/0000, which is address 8000H. When coupled with 1 0 0 for bits 15-12, if A12 through A0 are all 1 to find the upper end of the range, you get 1001/1111/1111/1111, which is address 9FFFH.

 

[wbishop256]

OOOOH! It's in groups of four! I figured it had to be 8 from 1000, but I didn't know where the fourth bit came from!

Where does the last letter in the chain, "H" come from?

 

[xnuke]

The H is a way of indicating each group of four digits is in hexadecimal.