
24.3.3 Refreshing the watchdog
A robust refreshing mechanism has been chosen for the watchdog. A valid refresh is a
write of 0xA602 followed by 0xB480 within 20 bus clock cycles to watchdog refresh
register. If these two values are written more than 20 bus cycles apart or if something
other than these two values is written to the register, a watchdog reset, or interrupt-then-
reset if enabled, is issued to the system. A valid refresh makes the watchdog timer restart
on the next bus clock. Also, an attempted unlock operation in between the two writes of
the refresh sequence goes undetected. See
Watchdog Operation with 8-bit access
for
guidelines related to 8-bit accesses to the refresh register.
24.3.4 Windowed mode of operation
In this mode of operation, a restriction is placed on the point in time within the time-out
period at which the watchdog can be refreshed. The refresh is considered valid only when
the watchdog timer increments beyond a certain count as specified by the watchdog
window register. This is known as refreshing the watchdog within a window of the total
time-out period. If a refresh is attempted before the timer reaches the window value, the
watchdog generates a reset, or interrupt-then-reset if enabled. If there is no refresh at all,
the watchdog times out and generates a reset or interrupt-then-reset if enabled.
24.3.5 Watchdog disabled mode of operation
When the watchdog is disabled through the WDOG_EN bit in the watchdog status and
control register, the watchdog timer is reset to zero and is disabled from counting until
you enable it or it is enabled again by the system reset. In this mode, the watchdog timer
cannot be refreshed–there is no requirement to do so while the timer is disabled.
However, the watchdog still generates a reset, or interrupt-then-reset if enabled, on a non-
time-out exception. See
Generated Resets and Interrupts
watchdog before enabling it. A system reset brings the watchdog out of the disabled
mode.
Functional overview
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
524
NXP Semiconductors
Содержание K22F series
Страница 2: ...K22F Sub Family Reference Manual Rev 4 08 2016 2 NXP Semiconductors...
Страница 150: ...Private Peripheral Bus PPB memory map K22F Sub Family Reference Manual Rev 4 08 2016 150 NXP Semiconductors...
Страница 168: ...Module clocks K22F Sub Family Reference Manual Rev 4 08 2016 168 NXP Semiconductors...
Страница 198: ...Security Interactions with other Modules K22F Sub Family Reference Manual Rev 4 08 2016 198 NXP Semiconductors...
Страница 258: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 258 NXP Semiconductors...
Страница 292: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 292 NXP Semiconductors...
Страница 398: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 398 NXP Semiconductors...
Страница 628: ...Initialization and application information K22F Sub Family Reference Manual Rev 4 08 2016 628 NXP Semiconductors...
Страница 740: ...Initialization Application Information K22F Sub Family Reference Manual Rev 4 08 2016 740 NXP Semiconductors...
Страница 750: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 750 NXP Semiconductors...
Страница 816: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 816 NXP Semiconductors...
Страница 866: ...Initialization Application Information K22F Sub Family Reference Manual Rev 4 08 2016 866 NXP Semiconductors...
Страница 890: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 890 NXP Semiconductors...
Страница 1028: ...Initialization Procedure K22F Sub Family Reference Manual Rev 4 08 2016 1028 NXP Semiconductors...
Страница 1040: ...Example configuration for chained timers K22F Sub Family Reference Manual Rev 4 08 2016 1040 NXP Semiconductors...
Страница 1118: ...Device mode IRC48 operation K22F Sub Family Reference Manual Rev 4 08 2016 1118 NXP Semiconductors...
Страница 1122: ...USB Voltage Regulator Module Signal Descriptions K22F Sub Family Reference Manual Rev 4 08 2016 1122 NXP Semiconductors...
Страница 1180: ...Initialization application information K22F Sub Family Reference Manual Rev 4 08 2016 1180 NXP Semiconductors...
Страница 1302: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 1302 NXP Semiconductors...
Страница 1374: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 1374 NXP Semiconductors...