When the PLL is active, the system clock frequency (SysClk) is calculated using the following
equation:
SysClk = f
VCO
/ (P 1)
The PLL system divisor factor (
PSYSDIV
) determines the value of the system clock. Table
5-6 on page 237 shows how the system divisor encodings affect the system clock frequency when
the f
VCO
= 480 MHz.
Table 27-17. System Divisor Factors for f
vco
=480 MHz
f
VCO
(MHz)= 480 MHz
System Clock (SYSCLK) (MHz)
System Divisors (P1)
a
4
120
8
60
10
48
16
30
20
24
40
12
80
6
a. The use of non-integer divisors introduce additional jitter which may affect interface performance.
If the main oscillator provides the clock reference to the PLL, the translation provided by hardware
and used to program the PLL is available for software in the
PLL Frequency n (PLLFREQn)
registers
(see page 292). The internal translation provides a translation within ± 1% of the targeted PLL VCO
frequency. Table 5-7 on page 238 shows the actual PLL frequency and error for a given crystal
choice.
Table 5-7 on page 238 provides examples of the programming expected for the
PLLFREQ0
and
PLLFREQ1
registers. The first column specifies the input crystal frequency and the last column
displays the PLL frequency given the values of
MINT
and
N
, when
Q
=0.
Table 27-18. Actual PLL Frequency
a
PLL Frequency
(MHz)
Reference
Frequency
(MHz)
b
N
MINT (Hexadecimal
Value)
MINT (Decimal
Value)
Crystal
Frequency
(MHz)
320
5
0x0
0x40
64
5
320
2
0x2
0x35
160
6
320
8
0x0
0x28
40
8
320
10
0x0
0x20
32
10
320
4
0x2
0x50
80
12
320
16
0x0
0x14
20
16
320
2
0x8
0xA0
160
18
320
20
0x0
0x10
16
20
320
8
0x2
0x28
40
24
320
5
0x4
0x40
64
25
480
5
0x0
0x60
96
5
480
6
0x0
0x50
80
6
480
8
0x0
0x3C
60
8
June 18, 2014
1836
Texas Instruments-Production Data
Electrical Characteristics