2.1.1 Updating Registers During Device Operation
If certain registers are changed while the device is in operation, it is possible for the PLL to become unresponsive (i.e. lose lock
indefinitely). Any change that causes the VCO frequency to change by more than 250 ppm since Power-up, NVM download, or
SOFT_RST requires the following special sequence of writes. The following are the affected registers:
Control
Register(s)
P0_NUM / P0_DEN
0x0208 – 0x0211
P1_NUM / P1_DEN
0x0212 – 0x021B
P2_NUM / P2_DEN
0x021C – 0x0225
P3_NUM / P3_DEN
0x0226 – 0x022F
Px_UPDATE
0x0230
P0_FRACN_MODE / P0_FRAC_EN
0x0231
P1_FRACN_MODE/ P1_FRAC_EN
0x0232
P2_FRACN_MODE / P2_FRAC_EN
0x0233
P3_FRACN_MODE/ P3_FRAC_EN
0x0234
MXAXB_NUM / MXAXB_DEN
0x0235 – 0x023E
MXAXB_UPDATE
0x023F
PLL lockup can easily be avoided by using the following the preamble and postamble write sequence when one of these registers is
modified during device operation. ClockBuilder Pro software adds these writes to the output file by default when Exporting Register
Files.
1. To start, write the preamble by updating the following control bits using Read/Modify/Write sequences:
Register
Value
0x0B24
0xC0
0x0B25
0x00
0x0540
0x01
2. Wait 625 ms for the device state to stabilize.
3. Then modify all desired control registers.
4. Write 0x01 to Register 0x001C (SOFT_RST) to perform a Soft Reset once modifications are complete.
5. Write the postamble by updating the following control bits using Read/Modify/Write sequences:
Register
Value
0x0540
0x00
0x0B24
0xC3
0x0B25
0x02
Si5386 Rev. E Reference Manual • Modes of Operation
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.2 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • December 9, 2021
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