23.3.5 Clock Prescaler Register (EWM_CLKPRESCALER)
This CLKPRESCALER register is reset to 0x00 after a CPU reset.
NOTE
This register can be written only once after a CPU reset.
Writing this register more than once generates a bus transfer
error.
NOTE
Write the required prescaler value before enabling the EWM.
NOTE
The implementation of this register is chip-specific. See the
Chip Configuration details.
Address: 4006_1000h base + 5h offset = 4006_1005h
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
0
0
0
0
0
0
0
0
EWM_CLKPRESCALER field descriptions
Field
Description
7–0
CLK_DIV
Selected low power source for running the EWM counter can be prescaled as below.
• Prescaled clock frequency = low power clock source frequency/ ( 1+ CLK_DIV )
23.4 Functional Description
The following sections describe functional details of the EWM module.
23.4.1 The EWM_out Signal
The EWM_out is a digital output signal used to gate an external circuit (application
specific) that controls critical safety functions. For example, the EWM_out could be
connected to the high voltage transistors circuits that control an AC motor in a large
appliance.
The EWM_out signal remains deasserted when the EWM is being regularly serviced by
the CPU within the programmable service window, indicating that the application code is
executed as expected.
Chapter 23 External Watchdog Monitor (EWM)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
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