Embedded development: embedded foundation -- the difference between restart and reset

　　 In use based on Eclipse Of IDE When debugging an embedded system , without doubt , The reader encountered reset and restart buttons in the debug perspective . At a high level , These two options may look the same , But there are important differences in when embedded developers should use restart instead of reset . Let's see how to use them in standard applications and when using boot loaders .

　　

 

　　 First , Let's discuss the basics and possible obvious issues . Pressing the reset button will cause the program to “ Power on reset ” Reset to application entry . When the reset button is pressed , Developers will find themselves in a processor reset handler . then , Developers can step through all the code , Including low-level initialization . After the application enters main A lot of things usually happen before .

　　 If developers don't care main What happened before , Just want to restart the application and return to main, They can press the restart button . Restart is a combined operation . Results with the developer pressing the reset key and then using the main The breakpoint in the first line performs the same operation . Restart is sometimes defined as an application starting from an entry point .( Please note that , This is different from the boot entry point ).

　　 secondly , For developers who use a single application in memory , Reset and restart seem almost the same , But if the developer has a boot loader and an application , That's what's interesting . During boot loader development , Embedded developers can use debugger commands to directly access the application code space . These commands may be similar to the following ：

　　set $sp = *0x280000

　　set $pc = *0x280004

　　set {int}0xe000ed08 = 0x280000

　　 These tell the debugger to set the stack pointer at startup 、 The program counter and interrupt vector table are set to a location other than the first location in memory . When executing these commands , Developers need to be aware of some interesting and useful things . The reset button still works as expected . Pressing it will return to the reset entry point , This will be the boot loader reset vector . however , If the developer presses the restart button , They will not reset after running . contrary , They will find themselves in the reset handler of the application code !

　　 Developers who work only in a single application space rarely notice any difference between reset and restart . in fact , Most of them tend to restart . Embedded developers working in environments with boot loaders still tend to reboot to debug and use their applications , But resetting will also provide them with a way to enter the boot loader and debug the combined boot loader / The method of application .