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17.3.4 Using interrupts to delay resets
When interrupts are enabled (CS1[INT] = 1), the watchdog first generates an interrupt
request upon a reset triggering event (such as a counter timeout or invalid refresh
attempt). The watchdog delays forcing a reset for 128 bus clocks to allow the interrupt
service routine (ISR) to perform tasks, such as analyzing the stack to debug code.
When interrupts are disabled (CS1[INT] = 0), the watchdog does not delay forcing a
reset.
17.3.5 Backup reset
NOTE
A clock source other than the bus clock must be used as the
reference clock for the counter; otherwise, the backup reset
function is not available.
The backup reset function is a safeguard feature that independently generates a reset in
case the main WDOG logic loses its clock (the bus clock) and can no longer monitor the
counter. If the watchdog counter overflows twice in succession (without an intervening
reset), the backup reset function takes effect and generates a reset.
17.3.6 Functionality in debug and low-power modes
By default, the watchdog is not functional in Active Background mode, Wait mode, or
Stop3 mode. However, the watchdog can remain functional in these modes as follows:
• For Active Background mode, set CS1[DBG]. (This way the watchdog is functional
in Active Background mode even when the CPU is held by the Debug module.)
• For Wait mode, set CS1[WAIT].
• For Stop3 mode, set CS1[STOP].
NOTE
The watchdog can not generate interrupt in Stop3 mode even if
CS1[STOP] is set and will not wake the MCU from Stop3
mode. It can generate reset during Stop3 mode.
Functional description
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
348
NXP Semiconductors
Summary of Contents for MC9S08PA4
Page 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
Page 2: ...MC9S08PA4 Reference Manual Rev 5 08 2017 2 NXP Semiconductors ...
Page 22: ...MC9S08PA4 Reference Manual Rev 5 08 2017 22 NXP Semiconductors ...
Page 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Page 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Page 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Page 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Page 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Page 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Page 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Page 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
Page 400: ...MC9S08PA4 Reference Manual Rev 5 08 2017 400 NXP Semiconductors ...