Software Watchdog Timers
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
21-15
— Reset mode (SWCRR[SWRI] = 1)
Software watchdog timer causes a hard reset (this is the default value after soft reset).
— Interrupt mode (SWCRR[SWRI] = 0)
Software watchdog timer causes a machine check interrupt to the core.
•
WDT prescaled/non-prescaled clock mode
The WDT counter clock can be prescaled by programming SWCRR[SWPR] bit that
controls the divide-by-65536 of WDT counter.
— Prescale mode (SWCRR[SWPR] = 1)
The WDT clock is divided by 65536.
— Non-prescale mode (SWCRR[SWPR] = 0)
The WDT clock is not prescaled.
21.3.3 Software WDT Servicing
The software watchdog timer service sequence consists of the following two steps:
•
Write 0x556C to the System Watchdog Service Register (SWSRR)
•
Write 0xAA39 to SWSRR
The service sequence reloads the watchdog timer and the timing process begins again. If a value
other than 0x556C or 0xAA39 is written to the SWSRR, the entire sequence must start over.
Although the writes must occur in the correct order before a time-out, any number of instructions
can be executed between the writes. This allows interrupts and exceptions to occur between the
two writes when necessary. Figure 21-5 shows a state diagram for the watchdog timer.
Figure 21-5. Software Watchdog Timer Service State Diagram
0x556C / Don’t reload
Reset
0xAA39 / Reload
State 0
Waiting for 0x556C
State 1
Waiting for 0xAA39
Not 0xAA39 / Don’t reload
Not 0x556C / Don’t reload
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...