Itech 1000

ITEC 1000 Assignment #2

Total = 100 marks (Solutions);

• 5 marks file name and general format

Instructions:

• All questions are based on Englander -- Chapters 6 & 7.

• Use a word processor (if you use a non-MS WORD compatible program, e.g., Pages, save as PDF or RTF).

• Both questions and answers must be appropriately formatted (including tables) and well presented with enough explanation.

• Be sure to name the file as your full name in the following format (lowercase), e.g., peggy_carter.docx

• Submit via the upload link provided at the course site any time before or by the deadline, March 26, 11 PM (sharp); late submissions will not be accepted.

• Apply the LMC instruction set below to answer relevant questions.

LMC Instruction Set Instruction Mnemonic Numeric Code Load LDA 5xx

Store STO 3xx

Add ADD 1xx

Subtract SUB 2xx

Input IN 901

Output OUT 902

End HLT 000

Branch/Jump BR 6xx

Branch if zero BRZ 7xx

Branch if zero or positive BRP 8xx

Data storage DAT xxx

1. Trace the program below and summarize what the program does; not a step-by-step

description of each instruction. [5 marks]

Address /

Mailbox #

Assembly /

Mnemonic

Numeric

Code

00 IN 901

01 STO 90 390

02 IN 901

03 STO 91 391

04 LDA 90 590

05 OUT 902

06 LDA 91 591

07 OUT 902

08 HLT 000

…

90 DAT 0 000

91 DAT 0 000

2. Complete the table below to construct an LMC program that will accept a set of three numbers

as INPUT and then add the first two numbers and output the answer, then subtract the first

number from the third and output the answer. The program begins at address 00 and data is

stored in address 90. [20 marks]

Mailbox # Mnemonic Numeric code Instruction Description

00 IN 901 Input first number

01

3. Complete the table below and construct an LMC program that will accept a number INPUT

and OUTPUT a sequence of numbers, starting at 1 and finishing with the INPUT

(maxNumber). The counter must be initialized to zero each time the program is run. The

program will continue (loop) until a 0 is entered. [20 marks]

Mailbox # Mnemonic

Numeric code Instruction Description

00 load zero (from 93) to the accumulator

01 Store the initial count

02 input

03 If zero, branch to halt

04 Store maxNumber

05 LoopTop load count

06 Add step to counter

07 Store count

08 Output

09 Subtract maxNumber

10 If positive, endLoop

11 Jumpt to loopTop

12 endLoop jump to start

13 Halt execution

90 step DAT 1

91 maxNumber DAT

92 count DAT

93 zero DAT

4. Complete the table below to construct an LMC program that will accept two INPUT numbers

and then OUTPUT the greater of the two. The program should begin at address 00 and data

should be stored in addresses beginning at 90. [25 marks]

Mailbox # Mnemonic Numeric code Instruction Description

5. Consider the LMC program below in which 2 numbers are entered and added.

Suppose the first input entry was stored in mailbox location 00.

a. Would the program have produced the same result? b. What would have happened if the program were executed a second time? c. What characteristic of the computer makes this true? [5 marks]

Mailbox Numeric

Address Code

00 901

01 306

02 901

03 106

04 902

05 000

06 000

6. If a computer has a 38-bit memory address register. How much memory can this computer

address? (Assume: 1 byte/cell; use the most appropriate measure unit). Show your work.

[5 marks]

Consider the following LMC instructions found in the given locations in memory.

Mailbox

Address

Mnemonic Code

15 LDA 40

16 ADD 41

…

40 723

41 021

7. Show the CPU Fetch/Execute cycle steps and the values of Instruction Register (IR), the

Program Counter (PC), the Memory Address Register (MAR), the Memory Data Register

(MDR), and Accumulator (A) when the instruction in address 15 is completed. [5 marks]

F/E cycle Register Values

8. Show the contents of each register as each step of the F/E cycle is performed for instruction

16 in the above program. [10 marks]

F/E cycle PC MAR MDR IR A

PC → MAR

MDR → IR

IR [address] → MAR

A + MDR → A

PC + 1 → PC