Intel NuPRO-850 GPIO Control Registers, The procedure of programming WDT, WDTTOUT# pin selection

5.1.2GPIO Control Registers

There are two GPIOs on Nupro-850 that relate to watchdog timer. They are listed below. The GPIO control base port is 480H.

WDT_TOUT# pin selection

WDT_TOUT# signal is multiplexed with GPIO32. When using WDT, this signal must be switched to WDT_TOUT# function. It used bit 0 of GPIOBASE + 30H to set WDT_TOUT function. (0 = WDT_TOUT#, 1 = GPIO32)

WDT LED Control

GPO25 of 6300ESB is designed to control WDT LED. Two features of WDT LED are supported on Nupro-850’s WDT LED lights or blinks.

WDT LED light

Set bit 25 of GPIOBASE + 04H to 0. Bit 25 of GPIOBASE + 0CH determines the state of WDT LED. (0 = light, 1 = dark)

WDT LED blink

Set bit 25 of GPIOBASE + 04H to 0. Bit 25 of GPIOBASE + 18H enables WDT LED blinking function. (0 = function normally, 1 = enable blinking) The high and low times have approximately 0.5 seconds each.

5.1.3The procedure of programming WDT

Step 1: Make sure WDT_TOUT# signal is workable. (Not GPIO32 function).

Step 2: Set WDT output enable, presecaler and interrupt type into WDT configuration register.

Step 3: Get control base from Base Address register.

Step 4: Program Preload register’s value according to unlocking sequence.

Step 5: Set WDT timer mode into WDT Lock Register.

Step 6: Enable WDT from WDT Lock register and program which functionality of WDT LED will be.

To keep the timer from causing an interrupt or driving WDT_TOUT#, the timer must be reloaded periodically. The frequency of reloads required is dependent on the value of the preload values. To reload the down-counter, the register unlocking sequence must be performed.

To disable WDT, Set bit 1 of WDT Lock Register to 0.

38 • Watchdog Timer