• Windowed refresh option
• Provides robust check that program flow is faster than expected.
• Programmable window.
• Refresh outside window leads to assertion of EWM_out.
• Robust refresh mechanism
• Write values of 0xB4 and 0x2C to EWM Refresh Register within 15
(EWM_refresh_time) peripheral bus clock cycles.
• One output port, EWM_out, when asserted is used to reset or place the external
circuit into safe mode.
• One Input port, EWM_in, allows an external circuit to control the assertion of the
EWM_out signal.
23.1.2
Modes of Operation
This section describes the module's operating modes.
23.1.2.1
Stop Mode
When the EWM is in stop mode, the CPU refreshes to the EWM cannot occur. On entry
to stop mode, the EWM’s counter freezes.
There are two possible ways to exit from Stop mode:
• On exit from stop mode through a reset, the EWM remains disabled.
• On exit from stop mode by an interrupt, the EWM is re-enabled, and the counter
continues to be clocked from the same value prior to entry to stop mode.
Note the following if the EWM enters the stop mode during CPU refresh mechanism: At
the exit from stop mode by an interrupt, refresh mechanism state machine starts from the
previous state which means, if first refresh command is written correctly and EWM
enters the stop mode immediately, the next command has to be written within the next 15
(EWM_refresh_time) peripheral bus clocks after exiting from stop mode. User must mask
all interrupts prior to executing EWM refresh instructions.
Introduction
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
510 NXP Semiconductors
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