MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
597
Preliminary—Subject to Change Without Notice
Chapter 20
Software Watchdog Timer (SWT)
20.1
Information Specific to This Device
This section presents device-specific parameterization and customization information not specifically
referenced in the remainder of this chapter.
20.1.1
Device-Specific Features
This device includes one SWT module.
The SWT can be clocked by either the system clock or crystal clock. Both clocks are connected to the SWT
and can be stopped by a bit on the SIU_HLT register.
The SWT can be configured to generate an interrupt upon watchdog time-out. The SWT interrupt is
‘ORed’ with the NMI signal from the SIU and routed to the NMI and Critical Interrupt inputs of the CPU;
see the SIU chapter for details.
The SWT includes an interrupt status bit so the ISR software can determine if the NMI request came from
the SWT or the external NMI pin.
20.1.2
Reset Assertion
The SWT can assert a reset when the watchdog timer expires. This reset will cause a system reset
equivalent to assertion of the RESET pin. Bit 6 of the Reset Status Register in the SIU indicates the SWT
as the source of the last reset.
20.1.3
Default Configuration
On this device, the SWT comes out of reset with the following default values:
•
CPU master access only, (MAPn = 0xFF)
•
Reset on Invalid (RIA = 1)
•
No window mode (WND = 0)
•
To cause a reset on timeout (ITR = 0)
•
No hard lock (HLK = 0)
•
Soft locked (SLK = 0),
•
Clocked from the crystal clock (CSL = 1)
•
Continues to run in STOP mode (STP = 0)
•
Stopped in debug mode (FRZ = 1)
•
Enabled (WEN = 1)
•
32.7 ms timeout for 8 MHz crystal
•
WATCHDOG_PERIOD timeout for 20 MHz crystal