Question
CS401- ComputerArchitecture and Assembly Language Programming
Assignment # 1
Fall 2009
Total Marks: 20
Due Date
Your assignment must be uploaded before or on17th Oct 2009.
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Objective
This assignment has been designed to enable you:
§ To understand how effective address iscalculated
§ To understand how physical memory address iscalculated
Assignment
Question_1: [marks: 6]
What is the effective address generated by each of the followinginstruction?
Initially BX=0x0100,label=0x0234, [label]=0x0010, andSI=0x00E1
(Offsets in part a, b and f are in decimal)
Question_2: [marks: 14]
Calculate the physical memory address generated by the followingsegment:offset pairs (both are hexadecimal values).
Explanation / Answer
Effective Address Ans1 mov ax, [bx+20] Effective Address = bx+20 Since Offset in a is Decimal so Decimal (20) = Hexadecimal (14) As Bx = 0100 =0100+0014 =0114
mov ax, [label+bx] Similarly Effective Add = [label+bx] Given the Label = 0234 and Bx= 0100 = 0234+0100 =0334 Similarly Effective Add = [label+bx] Given the Label = 0234 and Bx= 0100 = 0234+0100 =0334
mov ax, [bx + si] Effective Add = [bx + si] Since Bx = 0100 and Si = 00E1 =0100+00E1 =01E1 It can easily be done just follow the ins ntry to solve rest of the parts..
Ans2. Physical memory address 0000:0100 1st we are going to convert 16 bit Segment and 16 bitOffset address 0000:0100 respectively into 20 bit Address. 1st we are going to convert 16 bit Segment and 16 bitOffset address 0000:0100 respectively into 20 bit Address. i.e 20 bit Segment Address = 00000 20 bit Offset Address = 00100 Now calculating the physical Address 20 bit physical address in decimal is = 0000 00000001 0000 0000 20 bit physical address in hexadecimal = 00000 +00100 = 00100
0010:0000 Applying the same step of converting 16 bit into 20 bitaddresses we have 20 bit Segment Address = 00010 20 bit Offset Address = 00000 Calculating physical address by adding the both 20 bit physical address in hexadecimal is =00010+00000=00010 20 bit physical address in Decimal = 0000 0000 0000 00010000
DAD1:2345 16 bit Segment Address= (Converting from Hexadecimal to 16 bit binary form)DAD1 =1101 1010 1101 0001 Similarly 16 bit Offset Address = (Converting from Decimal to16 bit binary form)2345 = 0010 0011 0100 0101 Now converting Segment address from 16 to 20 bit form = 0DAD1=01101 1010 1101 001 Converting Offset Address from 16 to 29 bit form = 02345= 00010 0011 0100 0101 20 bit physical address in hexadecimal = 0DAD1+02345 =1ED04 20 bit physical address in decimal = 01101 1111 11010111 Try to solve rest of the parts n follow theinstructions.