S12 Clock, Reset and Power Management Unit (S12CPMU)
7.3.2
Register Descriptions
This section describes all the S12CPMU registers and their individual bits.
Address order is as listed in Figure 7-3.
7.3.2.1
S12CPMU Synthesizer Register (CPMUSYNR)
The CPMUSYNR register controls the multiplication factor of the PLL and selects the VCO frequency
range.
0x0034
7
6
5
4
3
2
1
0
R
W
VCOFRQ[1:0]
SYNDIV[5:0]
Reset
0
1
0
1
1
1
1
1
Figure 7-4. S12CPMU Synthesizer Register (CPMUSYNR)
Read: Anytime
Write: If PROT=0 (CPMUPROT register) and PLLSEL=1 (CPMUCLKS register), then write anytime.
Else write has no effect.
NOTE
Writing to this register clears the LOCK and UPOSC status bits.
f
= 2 × f
× (SYNDIV + 1)
If PLL has locked (LOCK=1)
VCO
REF
NOTE
must be within the specified VCO frequency lock range. Bus
f
VCO
frequency f must not exceed the specified maximum.
bus
The VCOFRQ[1:0] bits are used to configure the VCO gain for optimal stability and lock time. For correct
PLL operation the VCOFRQ[1:0] bits have to be selected according to the actual target VCOCLK
frequency as shown in Table 7-1. Setting the VCOFRQ[1:0] bits incorrectly can result in a non functional
PLL (no locking and/or insufficient stability).
Table 7-1. VCO Clock Frequency Selection
VCOCLK Frequency Ranges
VCOFRQ[1:0]
32MHz <= fVCO<= 48MHz
48MHz < fVCO<= 64MHz
Reserved
00
01
10
11
Reserved
S12P-Family Reference Manual, Rev. 1.13
206
Freescale Semiconductor
FREESCALE [ Freescale ]
