© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
User manual
Rev. 01 — 12 January 2006
30
Philips Semiconductors
UM10161
Volume 1
Chapter 3: System control block
The PLL inputs and settings must meet the following:
•
F
OSC
is in the range of 10 MHz to 25 MHz.
•
CCLK is in the range of 10 MHz to F
max
(the maximum allowed frequency for the
microcontroller - determined by the system microcontroller is embedded in).
•
F
CCO
is in the range of 156 MHz to 320 MHz.
3.8.10 Procedure for determining PLL settings
If a particular application uses the PLL, its configuration may be determined as follows:
1. Choose the desired processor operating frequency (CCLK). This may be based on
processor throughput requirements, need to support a specific set of UART baud
rates, etc. Bear in mind that peripheral devices may be running from a lower clock
than the processor (see
Section 3.11 “APB divider” on page 36
).
2. Choose an oscillator frequency (F
OSC
). CCLK must be the whole (non-fractional)
multiple of F
OSC
.
3. Calculate the value of M to configure the MSEL bits. M = CCLK / F
OSC
. M must be in
the range of 1 to 32. The value written to the MSEL bits in PLLCFG is M
−
1 (see
4. Find a value for P to configure the PSEL bits, such that F
CCO
is within its defined
frequency limits. F
CCO
is calculated using the equation given above. P must have one
of the values 1, 2, 4, or 8. The value written to the PSEL bits in PLLCFG is 00 for
P = 1; 01 for P = 2; 10 for P = 4; 11 for P = 8 (see
).
3.8.11 PLL configuring examples
Example:
an application configuring the PLL
System design asks for F
OSC
= 10 MHz and requires CCLK = 60 MHz.
Table 22:
PLL Divider values
PSEL Bits (PLLCFG bits [6:5])
Value of P
00
1
01
2
10
4
11
8
Table 23:
PLL Multiplier values
MSEL Bits (PLLCFG bits [4:0])
Value of M
00000
1
00001
2
00010
3
00011
4
...
...
11110
31
11111
32