SMC Networks 1232 Series Manual De Usuario

  

67 

 

 

 

67

 

 

The watchdog function resets the board at the end of the countdown. 
There are two ways to program the watchdog: 
 

• Using 

• Using 

direct Super I/O registers programming 

This method can be used under DOS or under Operating Systems using the board BIOS (i.e. not 
under Linux which erases the BIOS after the boot and autonomously manage the module 
hardware). 
The functions implemented from the BIOS are: 
 
INT 52h, function 0Ch:

 watchdog enabling with a fixed time of 2 seconds. This function programs 

and starts immediately the watchdog counter. 
 
INT 52h, function 0Dh:

 watchdog erasing. Counting is interrupted and watchdog disabled. 

 
INT 52h, function 0Eh

: watchdog refresh. Every call to this function restarts the counting from the 

initial value. 
 

  

When the watchdog is activated, the countdown starts immediately. If no refresh occurs, when 
the default timeout expires, the board reset is executed. So the watchdog must be enabled and 
continuously refreshed, avoiding in this way the board reset. 
 
Example: 
 
 ... 
 MOV 

AH, 

0Ch 

 

INT 

52h 

 

; Enable the watchdog (fixed timeout = 2 seconds) 

 ... 
 
 

 
This method must be used when the OS doesn’t manage the BIOS (i.e. Linux) or when a 
personalized watchdog programming is required.  
The following example shows how to change the Super I/O (SPIO) FDC 37B782 watchdog 
registers: 

 
; SPIO: enter in configuration mode ... 
 
 

MOV 

DX, 03F0h 

 

; SPIO Index Port