ZT5515A-1BW Intel, ZT5515A-1BW Datasheet - Page 42

• Manufacturer Part Number: ZT5515A-1BW
• Manufacturer: Intel

Specifications of ZT5515A-1BW

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Watchdog Timer
8.1.1
8.1.2
8.2
8.2.1
8.2.1.1
42
The watchdog is normally strobed by reading the Watchdog Register (79h), which clears the
counter. Writes to this register also clear the counter.
Power Up Initialization
The watchdog timer's logic is initialized at power up. This ensures that the STAGE1 MONITOR,
STAGE2 MONITOR, STAGE1 ENABLE, and STAGE2 ENABLE status and control bits power
up to unasserted states (0). This allows an application to determine if the reset was caused by a
watchdog timeout or a power up.
Timeout Values
The watchdog timer has a separate slow clock source that runs at a maximum frequency of 32 Hz
(25 Hz nominal). Because the clock is based on an RC oscillator, the nominal timeout period is
approximately 30 percent longer than the minimum value. The watchdog is guaranteed to timeout
in no less than the programmed minimum value.
Using the Watchdog in an Application
The following topics are provided to aid you in learning to use watchdog in an application. The
watchdog's Reset and NMI functions are described and sample code is provided.
Watchdog Reset and NMI are controlled through the watchdog Control and Status Register. See
Section C.1.2, “Watchdog (79h)” on page 78
Watchdog Reset
An application using the reset feature enables the watchdog reset, sets the terminal count period,
and then periodically strobes the watchdog to keep it from resetting the system. If a strobe is
missed, the watchdog times out and resets the system hardware.
Enabling the Watchdog Reset
C code for enabling the watchdog reset might look like the following:
#define WD_RESET_EN_BIT_SET0x20
void EnableWatchdogReset(void){
unsigned char WdValue;
WdValue = inb(WD_CSR_IO_ADDRESS);
WdValue |= WD_RESET_EN_BIT_SET;
outb(WD_CSR_IO_ADDRESS,WdValue);
Intel
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NetStructure
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ZT 5515 Compute Processor Board Technical Product Specification
for more information.
// Holds watchdog register
// values.
//
// Read the current contents
// of the watchdog register.
// Assert the enable bit in
// the local copy.
// Assert the enable in the
// watchdog register.