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Hi, I need to know how to use the WDT in the P89LPC932. I have selected its internal oscillator as the clock source. However, I do not know if it would consume more power than selecting the PCLK as its clock source. Also, how can I find out if the WDT is working fine. Do I need an infinite loop on this function? When do I call it? I have select WDTE = 1; and WDSE = 0; in the UCFG1 register. Sorry for so many questions, but I am still a beginner on this. Thank you void Watch_Dog (void) { EA = 0; WDCON = 0x05; //start WDT, and select WD oscillator WDL = 0xFF; WFEED1 = 0x0A5; //feed sequence WFEED2 = 0x05A; EA = 1; }
Erik below is the program I am using to test the WDT. I run it by using only the simulator and it worked fine (I think). This is the sample program "blinky" where port 2 shifts from right to left and left to right. The way I have it here is as follows: as soon as it finishes shifting from right to left, it initializes the WDT and after an overflow, occurs it resets the program. I am still a bit confused. What about in my real application when should I called or initialized the WDT. For what I understand the WDT should always overflow. If it does not (underflowing) then it means a software error while executing occured. therefore, the WDT will cause an system reset. Right? How can I keep a count of WDT underflowing... is there an interrupt for it, or just when it is used as a timer. If so what else should be included there. I have never worked with WDT before so this is new to me. Thanks for your help. #include <Reg932.h> #include <stdio.h> #include <String.h> UCFG1 = 0x88; void init(void); void brkrst_init(void); void Initialize_the_Puppy(void); #define KICK_THE_PUPPY WFEED1 = 0x0A5; WFEED2 = 0x05A; void delay (unsigned int cnt) { while (--cnt); } void Main(void) { brkrst_init(); { unsigned char i; P2M1 = 0; for(;;) { for (i = 0x01; i; i <<= 1) { P2 = i; // simulate running lights delay (50000); } Initialize_the_Puppy(); for (i = 0x80; i; i >>= 1) { P2 = i; delay (50000); } } } } void brkrst_init(void) // This function allows ISP entry through the UART break detect { //AUXR1 |= 0x40; // enable reset on break detect, pg. 102 SCON = 0x50; // select the BRG as UART baud rate source, pg. 60 SSTAT = 0x00; //Timer1 BRGR0 = 0x70; // 9600 BAUD at @ 7.373MHz internal RC oscillator BRGR1 = 0x04; BRGCON = 0x03; // enable BRG, pg. 59 } void Initialize_the_Puppy(void) { EA = 0; WDCON = 0x05; //start WDT, and select WD oscillator WDL = 0xFF; KICK_THE_PUPPY EA = 1; AUXR1 = 0x08; AUXR1 ^= ~0x08; while(1); // for test }
I am still a bit confused. What about in my real application when should I called or initialized the WDT. For what I understand the WDT should always overflow. If it does not (underflowing) then it means a software error while executing occured. therefore, the WDT will cause an system reset. Right? Feed the puppy or it bites The way a watchdog is used is that at strategic places in your program you feed it (feed sequence: see dxatasheet). If to much time passes between feeds a reset happens. Erik
Erik can you give me hints on where could be those strategic places in a program? Also, what about keeping track of the times when the WDT underflows...how would I do that. Thank you, you have been a great help.
Goto http://www.embedded.com and do a search on watchdog to access this and other nice articles on the subject. http://www.embedded.com/design_library/esd/hi/OEG20030115S0042 -Walt
can you give me hints on where could be those strategic places in a program how can I? it varies from program to program. Erik
can you give me hints on where could be those strategic places in a program NOT in ISRs, that will defeat the purpose Erik
That is good to know. Now I think I know where to use it. but what about keeping track of every time when the WDT underflows...how would you do that.
That is good to know. Now I think I know where to use it. but what about keeping track of every time when the WDT underflows...how would you do that 1) you have the softstart status bit 2) why would you want to, it never should Erik
Erik I lost you here! 1) you have the softstart status bit? What is that 2) why would you want to, it never should...I just want to keep a record of the times the WDT served the micro. Also, how many times should I call "initialize the puppy"...I mean the feeding process should be endless or just once. Thank you
Erik I lost you here! 1) you have the softstart status bit? What is that Please read the manual 2) why would you want to, it never should...I just want to keep a record of the times the WDT served the micro. look at the warmstart bit. Also, how many times should I call "initialize the puppy"... I mean the feeding process should be endless or just once. should be fed often enough not to time out