How to MCU programming with FS4500

[xupei]

Hello，

I have a question about MCU programming.

When in-vehicle programming without debug mode, the watchdog refresh can be disabled during INIT_FS state of the fail-safe logic. INIT_FS can be entered by a reset request with RSTB_REQ bit in SF_OUTPUT_REQUEST register.

QUESTION: if request a low pulse on the RSTb, MCU will reset?

[guoweisun]

Had already replied to you on case-00347803

[xupei]

你好，

可能我没说没明白，MCU刷新该如何操作FS4500？

我查看了AN5238，需通过SPI复位RSTB_REQ使其进入INIT模式；

可是，一旦RSTB置1，MCU也同步复位，MCU无法进行后续禁狗或刷新操作，这是我的疑惑。

谢谢！

[guoweisun]

我理解的是进入INIT_FS以后要再256ms内做一次refresh，所以留给MCU的时间就是reset以后256ms内进行refresh的操作

[xupei]

额，不好意思，没太明白这个programming sequence，问下，有programming demo不？

是不是需要programming时，watchdog无法disable?

我理解，FS45&MCU处于normal，收到programming请求时，如果需要RSTB复位，MCU也会同步复位，刷新请求将失效。

[guoweisun]

when MCU request SBC to reset, both SBC and MCU will be reset, then SBC go to INIT_FS mode and MCU start to run the code from the beginning after MCU reset recover to high. MCU will process INIT codes and have first watchdog within 256ms. it is the same process when the system start to run. 

[Shailendrag]

 @guoweisun But after Reset, how we will decide why this reset happen for reprogramming purpose or normal reset (As both SBC and MCU both are reset after writing RSTB_REQ bit in SF_OUTPUT_REGISTER) ?

For reprogramming : we have to disable the watchdog by writing WD_WINDOW_3:0= 0000

Normal Reset: We have to enable the watchdog ( By selecting watchdog window (3ms))

How to handle these two thing in SBC initialization part ?

Thanks