s3c2416 naked running environment configuration

I just started learning ARM-linux recently. I bought a tq2416 board last week. The Linux information given was too complicated and profound and I didn’t want to read it. I can’t wait to run the 2416. So I searched everywhere for relevant information on naked running, but there were really few people using 2416, and there was even less information on the Internet. The information on naked running was almost blank. Finally, I found a related post on amobbs http://www.amobbs.com/thread-5529091-1-1.html , and downloaded the code shared by Tifosi_ through my colleagues, and then through my own exploration, I finally realized s3c2416 Running naked, I would like to express my gratitude to Tifosi_ and my colleague Brother Yuan!

Debugging software environment: Keil uVision 4.7, special attention needs to be paid here. Some versions of Keil support s3c2416 Device, but cannot be compiled. For example, Keil uVision 4.1 will prompt that ARM926EJ-S is not supported.

Debugging tool: J-link V8

Target board: tq2416, of course it can also be other boards, the premise is to lead out the JTAG pins, all descriptions here take tq2416 as an example

Keil configuration: Download and install Keil uVision 4.7, create a new project, enter the target options dialog box to set the compilation environment, the main settings here are the Target option, Debug option and Utilities option

Target option settings

The 2416 SRAM is used for debugging here, but we seem to have made a mistake here, because the memory map provided in the 2416 user manual clearly indicates that the starting position of the SRAM is 0x40000000. In fact, I did make a mistake here, and it took me several days to find out. The first code started by 2416 is the program solidified in IROM. The address of IROM is 0x00000000. It is responsible for copying the startup code of the selected startup source to SRAM, and then forcibly mapping the SRAM address to 0x00000000. At this point, the IROM disappears and runs is the code in SRAM. Naturally, there is no more SRAM at 0x40000000. This SRAM, called Steppingstone, has a total space of 64KB. As shown in the figure above, the first 32KB is set as ROM, which is equivalent to program memory, and the last 32KB is set as RAM, which is data memory.

Debug option configuration

Here we mainly choose the debugging tool (J-LINK), and more importantly, add a configuration script file (as shown in the figure above. StartUpStart.ini file). This script file can make the CPU execute commands through J-LINK before debugging. Here The main purpose is to load the executable file and set the program execution starting address. The content of the script file is as follows:

1 FUNC void SetupForStart (void) 

2 {    

3     SP = 0x0000f000;

4     PC = 0x00000000;

5 }

6 LOAD .Objects3c2416.axf INCREMENTAL

7 SetupForStart();

Next set the Utilities options, refer to the picture below.

Utilities option configuration

After completing the above settings, save, and the compilation and debugging environment settings are completed. Next, you need to write a piece of code to verify whether 2416 can operate normally. The code is relatively simple. It is a small program written in assembly to calculate the sum of 1+...+100. In project "s3c2416", create a new "s3c2416_Add.s" file and write the following code:

 1             AREA    RESET, CODE, READONLY;, ALIGN = 3

 2             ARM

 3             ;PRESERVE8

 4 

 5     ENTRY

 6             

 7             LDR R0,=0x00            ;R0=0

 8             LDR R1,=0x00            ;R1=0

 9             LDR R2,=0x00008000      ;R2=0x00008000

10 ADDER       ADD R0,R0,#0x01         ;R0++

11             ADD R1,R1,R0            ;R1+=R0

12             CMP R0,#100             ;R0==100?LOOP:ADDER

13 FROG LOOP

14             B    ADDER

15 

16 STR R1,[R2] ;*(0x00008000)=R1

17 LOOP        B    LOOP                ;while(1);

18             END

The general idea of ​​the above code is: R0 is the counter, from 1 to 100; R1 is the accumulator, recording the result of each addition; R2 is a pointer pointing to 0x00008000, and the final result will be saved to the above address; when the program starts, Initialize the value of the register, then enter the loop accumulation. After the accumulation is completed, the result is saved to 0x00008000, and finally enters an infinite loop. Save the file and settings, compile, and start debugging if there are no errors. Before debugging, you need to ensure that the J-link driver is installed and connected to the JTAG port on the development board.

Debugging interface

Click the debug button to enter the debugging interface. Debugging starts. You can execute it step by step and observe the values ​​of each register and the execution steps of the program. The logic of the program is very simple, and it doesn't matter whether it is right or wrong. The most important significance is that s3c2416 can finally run naked!