Overview Program in LC-3 machine language Use the Editor Use LC-3 Simulator Trap Instruction

LC-3 Editor / Simulator Go to Authors’ Web page: Download: http://www.mhhe.com/patt2 Download: LC-3 Simulator – Win or Unix - (LC-3 Edit, LC-3 Simulate) LC-3 Simulator Lab Manual

Sum of 12 Integers Compute sum of 12 integers. Numbers start at location x3100. Program starts at location x3000. R1  x3100 R3  0 (Sum) R2  12(count) R2=0? R4  M[R1] R3  R3+R4 R1  R1+1 R2  R2-1 NO YES Write program

Sum integers from x3100 – x310B Address Instruction Comments x3000 1 1 1 0 0 0 1 0 1 1 1 1 1 1 1 1 R1  x3100 x3001 0 1 0 1 0 1 1 0 1 1 1 0 0 0 0 0 R3  0 x3002 0 1 0 1 0 1 0 0 1 0 1 0 0 0 0 0 R2  0 x3003 0 0 0 1 0 1 0 0 1 0 1 0 1 1 0 0 R2  12 x3004 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 1 If Z, goto x300A x3005 0 1 1 0 1 0 0 0 0 1 0 0 0 0 0 0 Load next value to R4 x3006 0 0 0 1 0 1 1 0 1 1 0 0 0 1 0 0 Add to R3 x3007 0 0 0 1 0 0 1 0 0 1 1 0 0 0 0 1 Increment R1 (pointer) X3008 0 0 0 1 0 1 0 0 1 0 1 1 1 1 1 1 Decrement R2 (counter) x3009 0 0 0 0 1 1 1 1 1 1 1 1 1 0 1 0 Goto x3004

The Add program in “binary” 0011000000000000 ;start x3000 1110001011111111 ;R1=x3100 0101011011100000 ;R3=0 0101010010100000 ;R2=0 0001010010101100 ;R2=R2+12 0000010000000101 ;If z goto x3009 0110100001000000 ;Load next value into R4 0001011011000100 ;R3=R3+R4 0001001001100001 ;R1=R1+1 0001010010111111 ;R2=R2-1 0000111111111010 ;goto x3004

The Add program in “hex” 3000 ;start x3000 E2FF ;R1=x3100 56E0 ;R3=0 54A0 ;R2=0 14AC ;R2=R2+12 0405 ;If z goto x3009 D840 ;Load next value into R4 16C4 ;R3=R3+R4 1261 ;R1=R1+1 14BF ;R2=R2-1 0FFA ;goto x3004

The Add program Data (hex) 3100 ; Begin data at x3100 3107 ; Loc x3100 2819 0110 0310 1110 11B1 0019 0007 0004 0000 0000 ; Loc x310B

LC3Edit Load the program into LC3Edit - Store it as prog.bin for a binary file, or Store it as prog.hex for a hex file - Create a prog.obj file with the Editor Load the data into LCEdit - Store it as data.bin for a binary file, or Store it as data.hex for a hex file - Create a data.obj file with the Editor

LC-3 Simulator Open LC-3 Simulator - Load prog.obj - Load data.obj - Set breakpoint(s) - Step through program

TRAP Calls a service routine, identified by 8-bit “trap vector.” When routine is done, PC is set to the instruction following TRAP. vector routine x23 input a character from the keyboard x21 output a character to the monitor x25 halt the program

TRAPS

Add HALT to “Add” program Add HALT statement and run program without breakpoint(s)

Example : Multiply Write program to Multiply two unsigned integers in R4 and R5

Example : Multiply This program multiplies two unsigned integers in R4 and R5. clear R2 add R4 to R2 decrement R5 R5 = 0? HALT No Yes Write program

Program to multiply [R4] x [R5] and place result in R2 x3200 Clear Accumulator (R2) R2 <- 0 x3201 Add [R4] to Accumulator R2 <- R2 + R4 x3202 Dec R5 R5 <- R5 – 1 x3203 Do again if [R5] > 0 BR p x3201 x3204 Stop HALT

Program to multiply [R4] x [R5] and place result in R2 Code program

Program to multiply [R4] x [R5] and place result in R2 x3200 Clear Accumulator (R2) R2 <- 0 0101 010 010 1 00000 54A0 x3201 Add [R4] to Accumulator R2 <- R2 + R4 0001 010 010 0 00 100 1484 x3202 Dec R5 R5 <- R5 – 1 0001 101 101 1 11111 1B7F x3203 Do again if [R5] > 0 BR p x3201 0000 001 111111101 03FD x3204 Stop HALT 1111 0000 00100101 F025 Test on Simulator

Write a program to place the absolute value of the [R2] in R2 How do we compute A = - A if we don’t have have a subtract instruction?

Example - # Occurrences of Inputted Char

Example - # Occurrences of Inputted Char Program (1 of 2) Address Instruction Comments x3000 0 1 0 1 0 1 0 0 1 0 1 0 0 0 0 0 R2  0 (counter) x3001 0 0 1 0 0 1 1 0 0 0 0 1 0 0 1 0 R3  M[x3102] (ptr) x3002 1 1 1 1 0 0 0 0 0 0 1 0 0 0 1 1 Input to R0 (TRAP x23) x3003 0 1 1 0 0 0 1 0 1 1 0 0 0 0 0 0 R1  M[R3] x3004 0 0 0 1 1 0 0 0 0 1 1 1 1 1 0 0 R4  R1 – 4 (EOT) x3005 0 0 0 0 0 1 0 0 0 0 0 0 1 1 1 0 If Z, goto x300E x3006 1 0 0 1 0 0 1 0 0 1 1 1 1 1 1 1 R1  NOT R1 x3007 0 0 0 1 0 0 1 0 0 1 1 0 0 0 0 1 R1  R1 + 1 X3008 0 0 0 1 0 0 1 0 0 1 0 0 0 0 0 0 R1  R1 + R0 x3009 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 1 If N or P, goto x300B

Example - # Occurrences of Inputted Char Program (2 of 2) Address Instruction Comments x300A 0 0 0 1 0 1 0 0 1 0 1 0 0 0 0 1 R2  R2 + 1 x300B 0 0 0 1 0 1 1 0 1 1 1 0 0 0 0 1 R3  R3 + 1 x300C 0 1 1 0 0 0 1 0 1 1 0 0 0 0 0 0 R1  M[R3] x300D 0 0 0 0 1 1 1 0 0 0 0 0 0 1 0 0 Goto x3004 x300E 0 0 1 0 0 0 0 0 0 0 0 1 0 0 1 1 R0  M[x3013] x300F 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 R0  R0 + R2 x3010 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 1 Print R0 (TRAP x21) x3011 1 1 1 1 0 0 0 0 0 0 1 0 0 1 0 1 HALT (TRAP x25) X3012 Starting Address of File x3013 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 ASCII x30 (‘0’)