Philips P89LPC908 External Clock Input Option P89LPC906, CPU Clock Cclk Wakeup Delay, Trim

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Philips Semiconductors

User’s Manual - Preliminary -

 

 

 

CLOCKS

P89LPC906/907/908

EXTERNAL CLOCK INPUT OPTION - P89LPC906

 

 

In this configuration, the processor clock is derived from an external source driving the XTAL1 / P3.1 pin. The rate may be from 0 Hz up to 12 MHz. The XTAL2 / P3.0 pin may be used as a standard port pin or a clock output.

.

TRIM

 

7

6

5

4

3

2

1

0

 

Address: 96h

 

 

 

 

-

ENCLK

TRIM.5

TRIM.4

TRIM.3

TRIM.2

TRIM.1

TRIM.0

 

Not bit addressable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset Source(s): Power-up only

 

 

 

 

 

 

 

 

 

 

Reset Value: On power-up reset, ENCLK = 0, and TRIM.5-0 are loaded with the factory programmed value.

 

 

BIT

SYMBOL

FUNCTION

 

 

 

 

 

 

 

 

TRIM.7

-

Reserved.

 

 

 

 

 

 

 

 

TRIM.6

ENCLK

When ENCLK =1, CCLK/ 2 is output on the XTAL2 pin (P3.0) provided that the crystal

 

 

oscillator is not being used. When ENCLK=0, no clock output is enabled (P89LPC906).

TRIM.5-0

 

Trim value.

 

 

 

 

 

 

 

 

Note: on reset, the TRIM SFR is initialized with a factory preprogrammed value. When setting or clearing the ENCLK bit, the user should retain the contents of bits 5:0 of the TRIM register. This can be done by reading the contents of the TRIM register (into the ACC for example), modifying bit 6, and writing this result back into the TRIM register. Alternatively, the "ANL direct" or "ORL direct" instructions can be used to clear or set bit 6 of the TRIM register.

Figure 2-2: On-Chip RC Oscillator TRIM Register

CPU CLOCK (CCLK) WAKEUP DELAY

The P89LPC906/907/908 has an internal wakeup timer that delays the clock until it stabilizes depending to the clock source used. If the clock source is any of the three crystal selections (P89LPC906), the delay is 992 OSCCLK cycles plus 60-100µs. If the clock source is either the internal RC oscillator or the Watchdog oscillator, the delay is 224 OSCCLK cycles plus 60-100µs.

CPU CLOCK (CCLK) MODIFICATION: DIVM REGISTER

The OSCCLK frequency can be divided down, by an integer, up to 510 times by configuring a dividing register, DIVM, to provide CCLK. This produces the CCLK frequency using the following formula:

CCLK frequency = fOSC / (2N) Where: fOSC is the frequency of OSCCLK

N is the value of DIVM.

Since N ranges from 0 to 255, the CCLK frequency can be in the range of fOSC to fOSC/510 ( for N =0, CCLK = fOSC) .

This feature makes it possible to temporarily run the CPU at a lower rate, reducing power consumption. By dividing the clock, the CPU can retain the ability to respond to events other than those that can cause interrupts (i.e. events that allow exiting the Idle mode) by executing its normal program at a lower rate. This can often result in lower power consumption than in Idle mode. This can allow bypassing the oscillator start-up time in cases where Power down mode would otherwise be used. The value of DIVM may be changed by the program at any time without interrupting code execution.

2003 Dec 8

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Contents User Manual Table of Contents Power-On reset code execution Brownout Detection Power-On Detection Power Reduction Modes103 List of Figures List of Figures P89LPC906 PIN ConfigurationsProduct Comparison Logic SymbolsOscillator Divider Block Diagram P89LPC906KB Code Flash CPUClock Block Diagram P89LPC907Uart Byte Data RAMData RAM Port Block Diagram P89LPC908PIN Descriptions P89LPC906 P1.2 PIN Descriptions P89LPC907P1.0 TxDRxD PIN Descriptions P89LPC908Keyboard Input P1.0 P1.5 P1.1Special function registers table P89LPC906 Special function registersMSB LSB Hex Special function registers table P89LPC907 CMP1 Cmpref TRIM.5 TRIM.4 TRIM.3 TRIM.2 TRIM.1 TRIM.0 WDCON# Special function registers table P89LPC908 KB2 KB6 KB5 KB4 TL0 Code Memory Organization Data SFRLOW Speed Oscillator Option P89LPC906 Enhanced CPUClock Definitions CPU Clock OscclkWatchdog Oscillator Option Oscillator Option SELECTION- P89LPC906Clock Output P89LPC906 ON-CHIP RC Oscillator OptionCPU Clock Cclk Modification Divm Register CPU Clock Cclk Wakeup DelayBIT Symbol Function External Clock Input Option P89LPC906Low freq LOW Power Select P89LPC906High freq Med freqCPU Clocks Interrupt Arbitration Flag Bits Address Enable Bits Priority RankingInterrupt Priority Structure Summary of Interrupts P89LPC906 DescriptionTI & RI External Interrupt InputsExternal Interrupt PIN Glitch Suppression Summary of Interrupts P89LPC907,P89LPC908 DescriptionBopd EBO Rtcf Kbif Interrupts RST Port ConfigurationsQUASI-BIDIRECTIONAL Output Configuration Number of I/O Pins Available Clock Source Reset OptionPort latch data Open Drain Output ConfigurationStrong Port latch data Port pin Input data Glitch rejection INPUT-ONLY ConfigurationPUSH-PULL Output Configuration Port 0 Analog FunctionsPort Output Configuration P89LPC906 Port Output Configuration P89LPC907Port Output Configuration P89LPC908 Ports Ports TMOD.3 TmodTMOD.7 TMOD.6TAMOD.7-1 Overflows. ModeMode Tamod P89LPC907Tcon THn TFn PclkT0C/T = Overflow TLn THn TFn Interrupt T0 Pin T0C/T = OverflowTimer Overflow Toggle Output P89LPC907 Pclk TL0TR0 ENT0 Pclk TH0 Timers 0 REAL-TIME Clock Source Divm Cclk FOSC2 FOSC1 FOSC0 RTCS10UCFG1.2 UCFG1.1 UCFG1.0 Cclk Frequency RTC Clock Frequency XclkExternal clock/DIVM RC Oscillator/DIVMWDT Oscillator/DIVM UndefinedReset Sources Affecting the REAL-TIME Clock Changing RTCS1-0REAL-TIME Clock INTERRUPT/WAKE UP Rtccon REAL-TIME CLOCK/SYSTEM Timer Brownout Detection POWER-ON Detection Power Reduction ModesBrownout Options Power Reduction Modes Pcon Pcona Power Monitoring Functions Modes UartSFR Locations for UARTs SFR SpaceBaud Rate Generator and Selection Updating the BRGR1 and BRGR0 SfrsFraming Error Break DetectBrgcon Scon Sstat More about Uart ModeSerial Port Mode 0 Double Buffering Must Be Disabled PCON.6 RB8 SMOD0 Framing Error and RI in Modes 2 and 3 with SM2 =FE and RI when SM2 = 1 in Modes 2 More about Uart Modes 2Double Buffering in Different Modes Double BufferingTransmission with and without Double Buffering 9TH BIT BIT 8 in Double Buffering Modes 1, 2Automatic Address Recognition Multiprocessor CommunicationsUart Uart Block Diagram of Reset POWER-ON Reset Code ExecutionRstsrc Comparator Configuration CIN1A CO1 CMP1 Cmpref Comparator and Power Reduction ModesInternal Reference Voltage Comparator InterruptComparator Configuration Example Analog Comparators Kbcon KbpatnKbmask Watchdog timer configuration Watchdog FunctionWdte Wdse Function Feed Sequence Wdcon PRE2-PRE0 P89LPC906/907/908 Watchdog Timeout ValuesControl register Watchdog Timer in Timer ModePrescaler Reset Pclk WatchdogCLK Power Down OperationWatchdog Clock Source PrescalerWatchdog Timer Watchdog Timer Software Reset Dual Data PointersAUXR1 MOVX@DPTR, a MOVCA, @A+DPTRMove code byte relative to Dptr to the accumulator MOVXA, @DPTRIntroduction to IAP-LITE FeaturesUsing Flash AS Data Storage General DescriptionFlash Program Memory Fmcon Assembly language routine to erase/program all or part of a Accessing Additional Flash ElementsERASE-PROGRAMMING Additional Flash Elements Reading Additional Flash ElementsUCFG1 Fmadrl Conf User Configuration Bytes UCFG1P89LPC906 Unprogrammed value 00h User Security BytesSECx Address xxxxhBootstat BootvecLogical ArithmeticData Transfer Mnemonic Description Bytes Cycles Hex CodeBranching BooleanMiscellaneous RetiB8-BF D8-DF2003 Dec Initial release 104 Index Dual Data Pointers Port 0 12, 13 SFR 109 P89LPC906/907/908
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