Miscellaneous registers (Misc)
RM0082
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Doc ID 018672 Rev 1
12.4.8 PLL_CLK_CFG
register
The PLL_CLK_CFG is an R/W register used to configure the input source clock for all the
internal PLLs. The register bit assignments is given in the next table.
Table 162.
PLL1/2_MOD register bit assignments
PLL1_MOD Register
PLL2_MOD
0x010
0x01C
Bit
Name
Reset
Value
Description
[31:29]
RFU
-
Reserved for future use (Write don’t care - Read return
zeros).
[28:16]
pll_modperiod
13’h0
MP(12:0) PLL modulation wave parameters:
Modulation rate f
mod
depends from reference clock f
ref;
and modulation period mp as detailed in the next formula
:
Example: If f
ref
= 24000 kHz and f
mod
= 100 kHz the
modulation period register will be mp=60.
Any changes in the reference clock results in changes in
the modulation frequency.
The maximum modulation frequency that can pass
through the filter is 100 kHz.
[15:00]
pll_slope
16’h0
SR(15:0) PLL slope modulation wave parameters:
The slope modulation rate reflects the modulation-depth
(md) in respect to the nominal frequency of the un-
dithered clock as shown in the next formula:
Where sr in the actual value of the slope register.
Example: If md=2.5% and f
VCD
= 576 MHz and f
mod
= 100
kHz with f
ref
= 24 MHz, (using the simplified formula) it
results:
f
mod
KHz
(
)
f
ref KHz
(
)
4
mp
•
---------------------
=
sr
2
17
f
ref
2
--------
md
f
VCD
•
•
f
mod
•
=
sr
2
8
mp
--------
md
M
•
•
=
sr
256
0
025
3072
•
•
•
60
------------------------------------------------------
327
0
0147
×
=
=
=