怎么通过PIC18F65 K80完成AN1310

大家好，我正试着通过PIC18F65 K80完成AN1310。此刻我正试图理解代码是如何工作的。我用MPLAB X IDE和MPASM（我使用1.05版）编译了PIC18引导加载程序的ASM代码，而令我惊讶的是，程序内存窗口只显示FFS。最初我怀疑有一个MPLAB X IDE怪癖，但过了一会儿，我意识到我只是在看程序内存的启动，而Bootloader实际上是在它的结尾写的。这是意料之中的，因为这是我想使用的设置（在程序内存结束时用Bootloader），但是我希望在重置向量上可以看到“Goto”或“BRA”指令。相反，重置向量只是PANNFF，因此没有指令。将AN1310的文本放在穆尔的监视下，我看到了这样的语句：主机PC Bootloader应用程序将写一个“Goto”作为复位向量（地址，000小时）的第一条指令。这个GOTO在启动时跳转到引导加载程序。应用固件的原始复位向量指令在内存引导程序块之前自动移动到驻留。Bootloader固件使用这个应用程序重置向量来启动应用程序，当不请求引导加载模式时（参见图10）。因此，这个预期的GOTO指令将由PC软件…StestReStimg编写，但是：1。为什么在Bootloader固件本身中不是硬编码的？2。在编程程序启动引导程序后，你第一次启动微操作时发生了什么？它是否执行NOP，直到到达内存的引导加载程序的开始？



      以下为原文

    Hi all,

I am trying to work my way through the AN1310 in conjuntction with a PIC18F65K80. At the moment I am at the stage of trying to understand how the code works.


I compiled the asm code of the PIC18 bootloader using MPLAB X IDE and mpasm (I am using version 1.05) and to my surprised I saw the program memory window as indicating FFs only. Initially I suspected an MPLAB X IDE quirk, but after a while I realized I was only looking at the beginnning of the program memory and the bootloader has actually been written at the end of it. That was as expected, as this is the setup  I wanted to use (with the bootloader at the end of program memory), but I would have expected to see a "goto" or "bra" instruction at the reset vector. Instead, the reset vector is just playn FF, so no instruction there. Putting the text of AN1310 under moore scrutiny, I came across this statements:

The host PC bootloader application will write a “GOTO” as the first instruction at the Reset vector (address, 0000h). This GOTO jumps to the bootloader at start-up. The application firmware’s original Reset vector instruction is automatically moved to reside just before the bootloader block of memory. The bootloader firmware uses this application Reset vector to start the application when the Bootloader mode is not requested (see Figure 10).

So it seems this expected goto instruction will be written by the PC software...insteresintg, but:

1. Why was not this hardcoded in the bootloader firmware itself?

2. What happends the first time you power up the micro after having programmed the bootloader with a programmer? Does it just execute NOPs until it reaches the beginning of the bootloader application towards the end of the memory?