Chapter 28
External Watchdog Monitor (EWM)
28.1 Introduction
For safety, a redundant watchdog system, External Watchdog Monitor (EWM), is
designed to monitor external circuits, as well as the MCU software flow. This provides a
back-up mechanism to the internal watchdog that resets the MCU's CPU and peripherals.
The watchdog is generally used to monitor the flow and execution of embedded software
within an MCU. The watchdog consists of a counter that if allowed to overflow, forces an
internal reset (asynchronous) to all on-chip peripherals and optionally assert the RESET
pin to reset external devices/circuits. The overflow of the watchdog counter must not
occur if the software code works well and services the watchdog to re-start the actual
counter.
The EWM differs from the internal watchdog in that it does not reset the MCU's CPU
and peripherals. The EWM provides an independent EWM_out signal that when asserted
resets or places an external circuit into a safe mode. The EWM_out signal is asserted
upon the EWM counter time-out. An optional external input EWM_in is provided to
allow additional control of the assertion of EWM_out signal.
28.1.1 Features
Features of EWM module include:
• Independent LPO_CLK clock source
• Programmable time-out period specified in terms of number of EWM LPO_CLK
clock cycles.
• Windowed refresh option
• Provides robust check that program flow is faster than expected.
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors
593
Summary of Contents for Kinetis KE1xZ256
Page 2: ...Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 2 NXP Semiconductors...
Page 178: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 178 NXP Semiconductors...
Page 356: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 356 NXP Semiconductors...
Page 410: ...Interrupts Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 410 NXP Semiconductors...
Page 604: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 604 NXP Semiconductors...
Page 634: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 634 NXP Semiconductors...
Page 674: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 674 NXP Semiconductors...
Page 820: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 820 NXP Semiconductors...
Page 1030: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1030 NXP Semiconductors...
Page 1052: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1052 NXP Semiconductors...
Page 1066: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1066 NXP Semiconductors...
Page 1268: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1268 NXP Semiconductors...
Page 1314: ...Usage Guide Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1314 NXP Semiconductors...
Page 1316: ...Kinetis KE1xZ256 Sub Family Reference Manual Rev 3 07 2018 1316 NXP Semiconductors...