1. SSST: CS130 F. Hadziomerovic
Von Neumann Concept (cont.): Instructions (ISA): format, addressing modes
Addressing modes: immediate (operand in instruction), register (reg in instruction, operand in register)
Memory (memory address/offset in instruction, operand in memory): PC-relative, Base+offset, indirect.
11/22/2005
SSST: CS130 F. Hadziomerovic

2. SSST: CS130 F. Hadziomerovic
Computer Architecture: Computer Architecture (Data Path) around single bus, signals
Ass#2
Question 3 Data Path: assume very simple computer with two registers A and B, that can perform
operations below.
A <- M[IR],
B <- M[IR],
A <- A + B,
A <- A – B,
M[IR] <- A
Draw the necessary data path (around single bus architecture) to carry these operations by showing
registers (including PC,IR, MAR, and MDR), adders, gates, etc. , data paths and control signals (with
arrowheads not filled in). (25 points) r
Memory w
LDMAR
MAR
MDR
LDMDR
MDRon
bus
PCon
IRon
Aon PC
LDIR IR
LDA A B
LDB
inv
invert
ALU +1
11/22/2005
SSST: CS130 F. Hadziomerovic

3. Programming Machine language programming: LC-3 editor, LC-3 simulator
Midterm
Question 5: Consider the program below: Translate the program to binary form (10 points). Interpret instructions
in mnemonic form (10 points). What does the program do? (5 points)
Address Content a. Binary b. Mnemonic
x x54A AND R2, R2, #0
x3001 x14AA ADD R2, R2, #10
x3002 xE2FD LEA R1, x3100
x3003 xF TRAP IN
x3004 x STR R0, R1, #0
x3005 x ADD R1, R1, #1
x3006 x14BF ADD R2, R2, # -1
x3007 x03FB BRp x3003
x3008 xF TRAP HALT
c. Program stores 10 input characters into 10 memory locations starting with x3100.
Question 5: Consider the program below: Translate the program to binary form (10 points). Interpret instructions
in mnemonic form (10 points). What does the program do? (5 points)
Address Content a. Binary b. Mnemonic
x3000 x AND R1, R1, #0
x3001 x126A ADD R1, R1, #10
x3002 xE40D LEA R2, x3010
x3003 x LDR R0, R2, #0
x3004 xF TRAP OUT
x3005 x14A ADD R2, R2, #1
x3006 x127F ADD R1, R1, #-1
x3007 x0BFB BRnp x3003
x3008 xF TRAP HALT
c. Prints the ASCII content of 10 consecutive memory locations starting with x3010.
11/22/2005
SSST: CS130 F. Hadziomerovic

4. SSST: CS130 F. Hadziomerovic
Programming (cont.): Problem solving and structured programming: Example page 139 Common bugs and debugging
Number of occurences (count): R2 <- 0
Input char from keyboard into R0: trap 23
Initialize pointer: R3 <- starting file address
Get char from file: R1 <- M[R3]
yes
Prepare output:
R0 <- R2 + x30
R1 ?= EOT no
yes
R0 ?= R1
Display char: trap 21
Incr.count
R2<-R2+1 no
halt: trap 25
Incr.point
R3<-R3+1
11/22/2005
SSST: CS130 F. Hadziomerovic

5. SSST: CS130 F. Hadziomerovic
Mnemonic program that displays how many times the keyed character shows in a file
X3000 AND R2,R2,#0 ; R2 < x x54A0
x3001 Trap x23 ; input char x xF023
x3002 LD R3, start file x x460E
X3003 LDR R1,R3,#0 ; get char x x62C0
X3004 ADD R4, R1, #-4 ; ‘eot’ = 4 x x187C
X3005 BRz x300D x x0407
X3006 NOT R1 x x927F
X3007 ADD R1,R1,#1 x x1261
X3008 ADD R1, R1, R0 x x1240
x3009 BRnp, x300B x x0A01
x300A ADD R2,R2,#1 x300A x14A1
x300B ADD R3, R3,#1 x300B x16E1
x300C BRnzp x x300C x0FF6
x300D LD R0, x x300D x2004
x300E ADD R0, R0, R2 ; ASCII count x300E x1002
X300F TRAP x21 ; display R0 x300F xF021
X3010 TRAP x25 ; halt x xF025
X3011 start address of a file x x3013
X ; ASCII_offset x x0030
11/22/2005
SSST: CS130 F. Hadziomerovic