1. ARMSim# and SWIInstructions Plug-in
Group 11:
Brian Knight
Benjamin Moore
Alex Williams

2. Outline Overview of SWIInstructions Plug-in for ArmSim#
Basic SWI Operations for I/O
Stdin/Stdout/Stderr View
ArmSim# I/O Examples with SWI
Printing Characters
Printing Strings
Determining Primes, Reading from Files and Printing to Files

3. SWIInstructions Plug-in Overview
Implements Software Interrupt Codes to allow for common I/O operations
Included in ARMSim# 1.91 Download
Enabled/Disabled via File->Preferences- >Plugins->SWIInstructions
Enabled by Default

4. Types of I/O Operations
Open/close files
Write characters and strings to Stdout or file
Reading from files and Stdin (Keyboard)
Allocate/deallocate memory on Heap
Interact with other Plug-ins (ex. Embest Board)

5. SWI Codes

6. SWI Codes
SWIcodes from 0 to 255 are forArmSim# I/O, codes above 255 are used for interaction with other ArmSim# plugin modules

7. How SWI Works Not really an exception or a proper interrupt
Enables the user to call routines in supervisor mode
Most ARM systems have a well-defined set of operations accessible through SWI

8. Outline Overview of SWIInstructions Plug-in for ArmSim#
Basic SWI Operations for I/O
Stdin/Stdout/Stderr View
ArmSim# I/O Examples with SWI
Printing Characters
Printing Strings
Determining Primes, Reading from Files and Printing to Files

9. Stdin/Stdout/Stderr View
Where output from user programs is displayed
Stdout: Output to file, pipe, or console
Stderr: Output stream for errors
Requests from Stdin freeze ARMSim# until input is received
Input is echoed in Stdin/Stdout/Stderr View

10. Stdin/Stdout/Stderr View

11. Example 1 – Printing Characters
.equ [symbol], [swi code] makes code more readable
swi 0x00: Display character stored in R0 to Stdout
swi 0x11: Halt execution
#’[char] uses ASCII value for character like an immediate value

12. Example 2 – Printing Strings
swi 0x02: Displays an ASCII string to Stdout (Address in R0)
String must be null-terminated (.asciz)
ASCII for “Hello World!\n” = 48,65,6C,6C,6F,20,57,6F,72,6C, 64,21,0A,00
Little-endian byte address assignment

13. Outline Overview of SWIInstructions Plug-in for ArmSim#
Basic SWI Operations for I/O
Stdin/Stdout/Stderr View
ArmSim# I/O Examples with SWI
Printing Characters
Printing Strings
Determining Primes, Reading from Files and Printing to Files

14. Example 3 – Is Prime

15. Questions?

16. References http://armsim.cs.uvic.ca/index.html
ARMSim_UserGuide4Plus.pdf
ARM system-on-chip architecture, second edition, Steve Furber, Addison Wesley, 2000      

17. Back-Up Slides

18. SWI Instructions step by step
SVC mode is entered
R15 is saved to R14_SVC
The IRQ disable bit is set
The PC is set to address & , this address has the instruction which jumps to the real SWI handler