1 / 13

LC-3 Assembly Language Programming Examples

LC-3 Assembly Language Programming Examples. Sample Program. Count the occurrences of a character in a file. Count the occurrences of a character in a file (1 0f 2). ; ; Program to count occurrences of a character in a file. ; Character to be input from the keyboard.

Leo
Download Presentation

LC-3 Assembly Language Programming Examples

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. LC-3Assembly LanguageProgramming Examples

  2. Sample Program • Count the occurrences of a character in a file.

  3. Count the occurrences of a character in a file (1 0f 2). ; ; Program to count occurrences of a character in a file. ; Character to be input from the keyboard. ; Result to be displayed on the monitor. ; Program only works if no more than 9 occurrences are found. ; ; ; Initialization ; .ORIG x3000 AND R2, R2, #0 ; R2 is counter, initially 0 LD R3, PTR ; R3 is pointer to character file GETC ; R0 gets input character LDR R1, R3, #0 ; R1 gets first character from file ; ; Test character for end of file ; TEST ADD R4, R1, #-4 ; Test for EOT (ASCII x04) BRz OUTPUT ; If done, prepare the output ; ; Test character for match. If a match, increment count. ; NOT R1, R1 ADD R1, R1, R0 ; If match, R1 = xFFFF NOT R1, R1 ; If match, R1 = x0000 BRnp GETCHAR ; If no match, do not increment ADD R2, R2, #1 ; ; Get next character from file. ; GETCHAR ADD R3, R3, #1 ; Point to next character. LDR R1, R3, #0 ; R1 gets next char to test BRnzp TEST

  4. Count the occurrences of a character in a file (2 of 2). ; ; Output the count. ; OUTPUT LD R0, ASCII ; Load the ASCII template ADD R0, R0, R2 ; Covert binary count to ASCII OUT ; ASCII code in R0 is displayed. HALT ; Halt machine ; ; Storage for pointer and ASCII template ; ASCII .FILL x0030 ; ASCII offset PTR .FILL x4000 ; PTR to character file .END

  5. Programming Exercise #1 Write a program to add the contents of R0 and R1, and indicate in R2 if there was an overflow • Flow Diagram • Assembly Code

  6. Programming Exercise #1 ; Add R3=R0+R1, R2=0 indicates no overflow ; .ORIG x3000 AND R2, R2, #0 ;Initially R2=0 (no Overflow assumed) ADD R3, R0, R1 ;R3=R0+R1 ; test for overflow ADD R0, R0, #0 ;test R0 BRN NEG ;Branch if RO negative ADD R1, R1, #0 ;test R1 BRN DONE ;No overflow if operand signs differ (R1 NEG) ADD R3, R3, #0 ;maybe, test R3 BRZP DONE ;No overflow if result sign matches (All POS) ADD R2, R2, #1 ;R2=1 indicating overflow NEG ADD R1, R1, #0 ;test R1 BRZP DONE ;No overflow if operand signs differ (R1 POS) ADD R3, R3, #0 ;maybe, test R3 BRN DONE ;No overflow if result sign matches (All NEG) ADD R2, R2, #1 ;R2=1 indicating overflow DONE HALT .END

  7. Programming Exercise #2 Write a program to count the 1’s in register R0 • Flow Diagram • Assembly code

  8. Programming Exercise #2 ; Program to count 1's in Register R0 ; R3 is a working copy of R0 ; R1 contains the count ; R2 is a loop counter .orig x3100 ADD R3, R0, #0 ;copy R0 into R3 AND R1, R1, #0 ;clear count ADD R3, R3, #0 ;test for Neg BRZP NEXT ;count if Neg ADD R1, R1, #1 NEXT AND R2, R2, #0 ;check remaining 15 bits ADD R2, R2, #-15 LOOP ADD R3, R3, R3 ;shift R3 left BRZP AGAIN ;count if Neg ADD R1, R1, #1 AGAIN ADD R2, R2, #1 ;loop until done BRN LOOP HALT .END

  9. Programming Exercise #3 Write a program to add two, two digit numbers read from the console • Flow Diagram • Assembly code

  10. ; Program to add two 2 digit decimal numbers read from the console ; R1 & R2 are working registers to load 2 digit number ; R3 is first number ; R4 is second number ; R5 is the sum ; R6 is conversion offset .orig x3600 LEA R0, MESSAGE ;print message PUTS ; Get first number LD R0, NEWLINE ;print PROMPT1 OUT OUT LEA R0, PROMPT1 PUTS GETC ;get first character OUT LD R6, M30 ;convert char to hex ADD R0, R0, R6 ADD R1, R0, R0 ;R1 = 2xR0 ADD R2, R1, #0 ;copy R1 into R2 ADD R2, R2, R2 ;R2 = 4xR0 ADD R2, R2, R2 ;R2 = 8xR0 ADD R2, R2, R1 ;R2 = 10xR0 GETC ;get second character OUT ADD R0, R0, R6 ;convert to hex ADD R3, R2, R0 ;R3 = first decimal number ; Get second number LEA R0, PROMPT2 ;get first character PUTS GETC OUT ADD R0, R0, R6 ;convert char to hex ADD R1, R0, R0 ;R1 = 2xR0 ADD R2, R1, #0 ;copy R1 into R2 ADD R2, R2, R2 ;R2 = 4xR0 ADD R2, R2, R2 ;R2 = 8xR0 ADD R2, R2, R1 ;R2 = 10xR0 GETC ;get second character OUT ADD R0, R0, R6 ;convert to hex ADD R4, R2, R0 ;R4 = first decimal number Programming Exercise #3

  11. ; Add the numbers and print results ADD R5, R4, R3 ;R5 = R3 + R4 LEA R0, SUM ;prepare to print results PUTS LD R4, P100 ;find 1st digit LD R3, M100 AND R0, R0, #0 LOOP1 ADD R0, R0, #1 ADD R5, R5, R3 ;subtract 100 until negative BRZP LOOP1 ADD R5, R5, R4 ADD R0, R0, #-1 LD R6, P30 ;convert to ascii & print ADD R0, R0, R6 OUT AND R0, R0, #0 ;find 2nd digit LOOP2 ADD R0, R0, #1 ADD R5, R5, #-10 ;subtract 10 until negative BRZP LOOP2 ADD R5, R5, #10 ADD R0, R0, #-1 LD R6, P30 ;convert to ascii & print ADD R0, R0, R6 OUT ADD R0, R5, R6 ;convert and print 3rd digit OUT LD R0, NEWLINE OUT HALT MESSAGE .STRINGZ "Enter two 2-digit decimal numbers:" NEWLINE .FILL x000A PROMPT1 .STRINGZ " The sum of " PROMPT2 .STRINGZ " and " SUM .STRINGZ " is " M30 .FILL xFFD0 ;-x30 P30 .FILL X0030 ; x30 M100 .FILL xFF9C ;-100 P100 .FILL x0064 ; 100 .END Programming Exercise #3 (2)

  12. Programming Exercise #4 Write a program to read characters from the keyboard, echo them on the console, and pack them into a file (2 characters per word) • Flow Diagram • Assembly code

  13. HW, due 11/14/07 • Write and test an LC-3 assembly language program to calculate and print all the numbers in the Fibonacci series that can be stored in words of the LC-3. The program should stop when it determines it has found the largest number. • Show: • A snapshot of your well commented Assembly program in the LC-3 Editor Window with the Assembly response. • A snapshot of the Simulator Console Display Window with the Fibonacci numbers displayed

More Related