UM10139

UM10139Chapter 3: System Control BlockRev. 01 — 15 August 2005User manual3.1 Summary of system control block functions3.2 Pin descriptionThe System Control Block includes several system features and control registers for anumber of functions that are not related to specific peripheral devices. These include:• Crystal Oscillator• External Interrupt Inputs• Miscellaneous System Controls and Status• Memory Mapping Control• PLL• Power Control• Reset• VPB Divider• Wakeup TimerEach type of function has its own register(s) if any are required and unneeded bits aredefined as reserved in order to allow future expansion. Unrelated functions never sharethe same register addressesTable 5 shows pins that are associated with System Control block functions.Table 5: Pin summaryPin name Pin Pin descriptiondirectionX1 Input Crystal Oscillator Input - Input to the oscillator and internal clockgenerator circuitsX2 Output Crystal Oscillator Output - Output from the oscillator amplifierEINT0 Input External Interrupt Input 0 - An active low/high level orfalling/rising edge general purpose interrupt input. This pin may beused to wake up the processor from Idle or Power-down modes.Pins P0.1 and P0.16 can be selected to perform EINT0 function.EINT1 Input External Interrupt Input 1 - See the EINT0 description above.Pins P0.3 and P0.14 can be selected to perform EINT1 function.Important: LOW level on pin P0.14 immediately after reset isconsidered as an external hardware request to start the ISPcommand handler. More details on ISP and Serial Boot Loader canbe found in "Flash Memory System and Programming" chapter onpage 291.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 16