The EWM_out signal is asserted in any of the following conditions:
• Servicing the EWM when the counter value is less than CMPL value.
• If the EWM counter value reaches the CMPH value, and no EWM service has
occurred.
• Servicing the EWM when the counter value is more than CMPL and less than CMPH
values and EWM_in signal is asserted.
• If functionality of EWM_in pin is enabled and EWM_in pin is asserted while
servicing the EWM.
• After any reset (by the virtue of the external pull-down mechanism on the EWM_out
pin)
On a normal reset, the EWM_out is asserted. To deassert the EWM_out, set EWMEN bit
in the CTRL register to enable the EWM.
If the EWM_out signal shares its pad with a digital I/O pin, on reset this actual pad defers
to being an input signal. It takes the EWM_out output condition only after you enable the
EWM by the EWMEN bit in the CTRL register.
When the EWM_out pin is asserted, it can only be deasserted by forcing a MCU reset.
Note
EWM_out pad must be in pull down state when EWM
functionality is used and when EWM is under Reset.
23.4.2 The EWM_in Signal
The EWM_in is a digital input signal that allows an external circuit to control the
EWM_out signal. For example, in the application, an external circuit monitors a critical
safety function, and if there is fault with this circuit's behavior, it can then actively initiate
the EWM_out signal that controls the gating circuit.
The EWM_in signal is ignored if the EWM is disabled, or if INEN bit of CTRL register
is cleared, as after any reset.
On enabling the EWM (setting the CTRL[EWMEN] bit) and enabling EWM_in
functionality (setting the CTRL[INEN] bit), the EWM_in signal must be in the deasserted
state prior to the CPU servicing the EWM. This ensures that the EWM_out stays in the
deasserted state; otherwise, the EWM_out pin is asserted.
Functional Description
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
508
Freescale Semiconductor, Inc.
