EWM Peripheral and Driver Overview

Content including 1) peripheral features, work logic and work method; 2) driver design logic and use method; 3) typical use case. More...

Peripheral feature and how this peripheral works

Features

• Independent LPO_CLK clock source
• Programmable time-out period specified in terms of number of EWM LPO_CLK clock cycles.
• Robust Windowed refresh
• 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
• EWM counter will freeze in STOP/WAIT mode, work in RUN mode.

How this driver is designed to make this peripheral work

This driver provides interfaces to initialize the EWM peripheral, then user can enable/disable interrupt on demand. For watch dog, there's a refresh function to reload it.

How to use this driver

• Use EWM_Init() to enable all EWM features on demand. The EWM_GetDefaultConfig() help user to get basic setting of this peripheral, user also can modify ewm_config_t in line with the actual case.
• With bEnableInterrupt of ewm_config_t user can choose to enable/disable EWM interrupt when this peripheral is initialized, EWM_EnableInterrupt() and EWM_DisableInterrupt() help user to enable/disable EWM interrupt after EWM_Init() has been called.
• EWM_Refresh() can reload the watch dog count which is very common function for all similar peripheral.
• The bEnableEwmInput and eSetInputAssertLogic of ewm_config_t can enable the EWM_in signal control the assert of EWM_out.

Typical Use Case

EWM is used to monitor the flow and execution of embedded software within an MCU, refresh operation should be periodically done, if the EWM is not refreshed in specified time window, EWM_Out signal will be asserted to to reset or place the external circuit into safe mode.

App_Function
{
  EWM_GetDefaultConfig(&sConfig);
  EWM_Init(EXAMPLE_EWM, &sConfig);
  xxxxx //set up periodical timer to refresh EWM
  if(timerISR) // when timer interrupt happens, refresh EWM
  {
      EWM_Refresh(EXAMPLE_EWM);
  }
}