Table 12.122. Register 0x0521 PLL M Divider Fractional Enable
Reg Address
Bit Field
Type
Name
Description
0x0521
3:0
R/W
M_FRAC_MODE
M feedback divider frac-
tional mode.
Must be set to 0x0B for
proper operation
0x0521
4
R/W
M_FRAC_EN
M feedback divider frac-
tional enable.
0: Integer-only division
1: Fractional (or integer)
division - Required for
DCO operation.
0x0521
5
R/W
Reserved
Must be set to 1
Table 12.123. Register 0x052A Manual Input Clock Select
Reg Address
Bit Field
Type
Name
Description
0x052A
0
R/W
IN_SEL_REGCTRL
Manual Input Select control source.
0: Pin controlled input clock selec-
tion (default)
1: IN_SEL register input clock se-
lection
(ZDM_IN_SEL in ZDM)
0x052A
3:1
R/W
IN_SEL
Manual Input Select selection reg-
ister. (Non-ZDM)
0: IN0 (default), 1: IN1, 2: IN2, 3:
IN3/FB_IN
4-7: Reserved
Note that in ZDM, the ZDM_IN_SEL (0x0487[2:1]) input source select control bits are used and IN_SEL is ignored. In both ZDM and
non-ZDM operation, IN_SEL_REGCTRL determines whether register-based or pin-based manual source selection is used.
Table 12.124. Register 0x052B Fastlock Control
Reg Address
Bit Field
Type
Name
Description
0x052B
0
R/W
FASTLOCK_AUTO_EN
Auto Fastlock Enable/Disable.
0: Disable Auto Fastlock
1: Enable Auto Fastlock (default)
0x052B
1
R/W
FASTLOCK_MAN
Manually Force Fastlock.
0: Normal Operation (default)
1: Force Fastlock
When Fastlock is enabled by either manual or automatic means, the higher Fastlock bandwidth will be used to provide faster settling of
the DSPLL. With FASTLOCK_MAN=0 and FASTLOCK_AUTO_EN=1, the DSPLL will automatically revert to the loop bandwidth when
the loop has locked and LOL de-asserts. See
for more information on Fastlock behavior.
Si5386 Rev. E Reference Manual • Register Map
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