MCF5253 Reference Manual, Rev. 1
Freescale Semiconductor
4-1
Chapter 4
Phase-Locked Loop and Clock Dividers
This chapter provides detailed information about the operation and programming of the clock generation
module as well as the recommended circuit settings. It also describes the audio clock generation and the
system power states.
4.1
PLL Features
•
The PLL locks to the crystal clock at the CRIN pin and produces a processor clock (PSTCLK) and
a SYSCLK which is always 1/2 of the processor clock.
•
The audio clock (AUDIOCLK) can be derived directly from CRIN or from the
LRCK3/AUDIOCLK/GPIO43 input pin.
•
The Audio DAC Master clocks MCLK1 and MCLK2 are derived directly from CRIN.
•
The PLL is configured by writing to a configuration register.
•
The PLL Configuration Register must always be programmed to Bypass mode before it is
reprogrammed to change any clock frequency. In bypass mode, the crystal clock is fed to the
processor (PSTCLK).
•
When the PLL is switched from “bypass” to “normal operation”, the switch-over is delayed until
the PLL is locked.
•
The MCF5253 has a new block added to the output of the PLL / Clock Dividers to provide
glitch-free Dynamic Clock Switching. This allows dynamic switching of the clock rate being fed
to the CPU core and the system bus. This new block is controlled by a new 32-bit register called
the ClockRate Register.
shows the PLL module and the frequency relationships of various clock signals.
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...