Phase-Locked Loop and Clock Dividers
MCF5253 Reference Manual, Rev. 1
4-4
Freescale Semiconductor
1. If this bit is 0, the PLL is by-passed, and CRIN is sent directly to the CPU and MCLKs. Always set the PLL to Bypass mode
before changing any other bit in this register. Clock frequencies described in other notes are only valid when this bit is set 1.
2. PLL may require up to 10 mS to lock
3. Fin is input frequency to PLL. Nominal setting for CRsel is ‘1’ for 33.8688 MHz X-tal, ‘0’ for 16.9344 MHz or 11.2896MHz X-tal.
4. Faudio is clock for audio interfaces. Typically 11.2896 or 16.9344 or 22.579 or 33.8688 MHz.
5. Fvcxo = Fin
×
(2
×
VCXODIV)/ (PLLDIV)
6. FVCXOOut depends on Fvcxo (note 5) and vcxoout setting as shown in
7. Field determines frequency output on MCLK1 and MCLK2 pins
When frequency is CRIN/2 or CRIN/4, duty cycle is 50%. When frequency is CRIN/3, duty cycle is 33%.
8. Fcpu = FVCXOOUT / CPUDIV; Fcpu is the frequency the processor is running at.
1
Reserved, should be cleared.
–
0
PLLBYP
0 Bypass PLL and dividers
1 Switch to PLL after PLL is locked
1, 2
Table 4-3. Vcxoout Settings
Vcxoout
Setting
FVCXOOut
0
Don’t use
1
Fvcxo
2
Fvcxo/2
3
Don’t use
Table 4-4. Crsel and CLsel Settings
Crsel
CLsel
Frequency
MCLK1
Frequency
MCLK2
0
000
CRIN
CRIN/2
0
001
CRIN
CRIN
0
010
CRIN/2
CRIN/2
0
011
CRIN/2
CRIN
1
000
CRIN/2
CRIN/2
1
001
CRIN/2
CRIN/3
1
010
CRIN/2
CRIN/4
1
011
CRIN/3
CRIN/2
1
100
CRIN/3
CRIN/3
1
101
CRIN/3
CRIN/4
1
110
CRIN/4
CRIN/2
1
111
CRIN/4
CRIN/3
Table 4-2. PLLCONFIG Field Descriptions (continued)
Field
Description
Notes
Summary of Contents for MCF5253
Page 1: ...Document Number MCF5253RM Rev 1 08 2008 MCF5253 Reference Manual...
Page 26: ...MCF5253 Reference Manual Rev 1 xxvi Freescale Semiconductor...
Page 32: ...MCF5253 Reference Manual Rev 1 xxxii Freescale Semiconductor...
Page 46: ...MCF5253 Introduction MCF5253 Reference Manual Rev 1 1 14 Freescale Semiconductor...
Page 62: ...Signal Description MCF5253 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 98: ...Instruction Cache MCF5253 Reference Manual Rev 1 5 10 Freescale Semiconductor...
Page 104: ...Static RAM SRAM MCF5253 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 128: ...Synchronous DRAM Controller Module MCF5253 Reference Manual Rev 1 7 24 Freescale Semiconductor...
Page 144: ...Bus Operation MCF5253 Reference Manual Rev 1 8 16 Freescale Semiconductor...
Page 176: ...System Integration Module SIM MCF5253 Reference Manual Rev 1 9 32 Freescale Semiconductor...
Page 198: ...Analog to Digital Converter ADC MCF5253 Reference Manual Rev 1 12 6 Freescale Semiconductor...
Page 246: ...DMA Controller MCF5253 Reference Manual Rev 1 14 18 Freescale Semiconductor...
Page 282: ...UART Modules MCF5253 Reference Manual Rev 1 15 36 Freescale Semiconductor...
Page 344: ...Audio Interface Module AIM MCF5253 Reference Manual Rev 1 17 46 Freescale Semiconductor...
Page 362: ...I2 C Modules MCF5253 Reference Manual Rev 1 18 18 Freescale Semiconductor...
Page 370: ...Boot ROM MCF5253 Reference Manual Rev 1 19 8 Freescale Semiconductor...