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Address: 4007_2000h base + 140h offset = 4007_2140h
Bit
7
Read
CLOCK_
RECOVER_
Write
EN
Reset
0
Field
7
Crystal-less USB enable
CLOCK_
This bit must be enabled if user wants to use the crystal-less USB mode for the Full Speed USB controller
RECOVER_EN
and transceiver.
NOTE: This bit should not be set for USB host mode or OTG.
0
Disable clock recovery block (default)
1
Enable clock recovery block
6
Reset/resume to rough phase enable
RESET_
The clock recovery block tracks the IRC48Mhz to get an accurate 48Mhz clock. It has two phases after
RESUME_
user enables clock_recover_en bit, rough phase and tracking phase. The step to fine tune the IRC 48Mhz
ROUGH_EN
by adjusting the trim fine value is different during these two phases. The step in rough phase is larger than
that in tracking phase. Switch back to rough stage whenever USB bus reset or bus resume occurs.
0
Always works in tracking phase after the 1st time rough to track transition (default)
1
Go back to rough stage whenever bus reset or bus resume occurs
5
Restart from IFR trim value
RESTART_
IRC48 has a default trim fine value whose default value is factory trimmed (the IFR trim value). Clock
IFRTRIM_EN
recover block tracks the accuracy of the clock 48Mhz and keeps updating the trim fine value accordingly
0
Trim fine adjustment always works based on the previous updated trim fine value (default)
1
Trim fine restarts from the IFR trim value whenever bus_reset/bus_resume is detected or module
enable is desasserted
4–3
This field is reserved.
Reserved
2
This field is reserved.
Reserved
This bit is for Freescale use only. Customers should not change this bit from its default state.
1
This field is reserved.
Reserved
This bit is for Freescale use only. Customers should not change this bit from its default state.
0
This field is reserved.
Reserved
Default should not be changed
33.5.24 IRC48M oscillator enable register
(USBx_CLK_RECOVER_IRC_EN)
Controls basic operation of the on-chip IRC48M module used to produce nominal
48MHz clocks for USB crystal-less operation and other functions.
Freescale Semiconductor, Inc.
6
5
RESET_
RESTART_
RESUME_
IFRTRIM_
ROUGH_EN
EN
0
0
USBx_CLK_RECOVER_CTRL field descriptions
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Chapter 33 Universal Serial Bus (USB) FS Subsystem
4
3
Reserved
Reserved
0
0
Description
2
1
Reserved
Reserved
0
0
0
0
559
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