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System Control Registers
252
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
System Control
4.2.19 PLLFREQ0 Register (Offset = 0x160) [reset = 0x0]
PLL Frequency 0 (PLLFREQ0)
This register always contains the variables used to configure the PLL. If the PLL is reprogrammed, it must
go through a relock sequence which is defined by the parameter t
READY
in the device-specific data sheet.
When controlling this register directly, software must change this value while the PLL is powered down.
Writes to PLLFREQ0 are delayed from affecting the PLL until the RSCLKCFG register NEWFREQ bit is
written with a 1.
The PLL frequency can be calculated using
.
f
VCO
= (f
IN
× MDIV)
where
•
f
IN
= f
XTAL
/ (Q+1)(N+1) or f
PIOSC
/ (Q+1)(N+1)
•
MDIV = MINT + (MFRAC / 1024)
(3)
The Q and N values are programmed in the PLLFREQ1 register. To reduce jitter, program MFRAC to 0x0.
PLLFREQ0 is shown in
and described in
.
Return to
Figure 4-25. PLLFREQ0 Register
31
30
29
28
27
26
25
24
RESERVED
R-0x0
23
22
21
20
19
18
17
16
PLLPWR
RESERVED
MFRAC
R/W-0x0
R-0x0
R/W-0x0
15
14
13
12
11
10
9
8
MFRAC
MINT
R/W-0x0
R/W-0x0
7
6
5
4
3
2
1
0
MINT
R/W-0x0
Table 4-31. PLLFREQ0 Register Field Descriptions
Bit
Field
Type
Reset
Description
31-24
RESERVED
R
0x0
23
PLLPWR
R/W
0x0
PLL Power.
This bit controls power to the PLL. If set, the PLL power is applied
and the PLL oscillates based on the values in the PLLFREQ0 and
PLLFREQ1 registers.
22-20
RESERVED
R
0x0
19-10
MFRAC
R/W
0x0
PLL M Fractional Value
9-0
MINT
R/W
0x0
PLL M Integer Value.
This field contains the integer value of the PLL M value.