UM10139

Philips SemiconductorsVolume 1UM10139Chapter 3: System Control Blockthe microcontroller. The same concern is present with the PLL1 and the USB. Theprotection is accomplished by a feed sequence similar to that of the Watchdog Timer.Details are provided in the description of the PLLFEED register.Both PLLs are turned off and bypassed following a chip Reset and when by enteringPower-down mode. The PLL is enabled by software only. The program must configure andactivate the PLL, wait for the PLL to Lock, then connect to the PLL as a clock source.3.8.1 Register descriptionThe PLL is controlled by the registers shown in Table 15. More detailed descriptionsfollow.Warning: Improper setting of the PLL0 and PLL1 values may result in incorrectoperation of the device and the USB module!Table 15:GenericnamePLLCONPLLCFGPLLSTATPLLFEEDPLL registersDescription Access Resetvalue [1]PLL Control Register. Holding register forupdating PLL control bits. Values written to thisregister do not take effect until a valid PLL feedsequence has taken place.PLL Configuration Register. Holding register forupdating PLL configuration values. Valueswritten to this register do not take effect until avalid PLL feed sequence has taken place.PLL Status Register. Read-back register for PLLcontrol and configuration information. IfPLLCON or PLLCFG have been written to, but aPLL feed sequence has not yet occurred, theywill not reflect the current PLL state. Readingthis register provides the actual valuescontrolling the PLL, as well as the status of thePLL.PLL Feed Register. This register enablesloading of the PLL control and configurationinformation from the PLLCON and PLLCFGregisters into the shadow registers that actuallyaffect PLL operation.System clock(PLL0)Address & NameR/W 0 0xE01F C080PLL0CONR/W 0 0xE01F C084PLL0CFGRO 0 0xE01F C088PLL0STATWO NA 0xE01F C08CPLL0FEEDUSB 48 MHzclock (PLL1)Address & Name0xE01F C0A0PLL1CON0xE01F C0A4PLL1CFG0xE01F C0A8PLL1STAT0xE01F C0ACPLL1FEED[1] Reset value reflects the data stored in used bits only. It does not include reserved bits content.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 28