Philips P89LPC906, P89LPC908, P89LPC907 user manual Open Drain Output Configuration, Port latch data

Page 36

Philips Semiconductors	User’s Manual - Preliminary -

I/O PORTS	P89LPC906/907/908

The third pullup is referred to as the "strong" pullup. This pullup is used to speed up low-to-high transitions on a quasi-bidirectional port pin when the port latch changes from a logic 0 to a logic 1. When this occurs, the strong pullup turns on for two CPU clocks quickly pulling the port pin high .

The quasi-bidirectional port configuration is shown in Figure 4-1.

Although the P89LPC906/907/908 is a 3V device the pins are 5V-tolerant (except for XTAL1 and XTAL2). If 5V is applied to a pin configured in quasi-bidirectional mode, there will be a current flowing from the pin to VDD causing extra power consumption. Therefore, applying 5V to pins configured in quasi-bidirectional mode is discouraged.

A quasi-bidirectional port pin has a Schmitt-triggered input that also has a glitch suppression circuit. (Please refer to the P89LPC906/907/908 datasheet, AC Characteristics for glitch filter specifications)

VDD

VDD

VDD

port latch data

2 CPU

clock delay

strong

very

weak

weak

port

pin

input data

glitch rejection

Figure 4-1: Quasi-Bidirectional Output

OPEN DRAIN OUTPUT CONFIGURATION

The open drain output configuration turns off all pullups and only drives the pulldown transistor of the port pin when the port latch contains a logic 0. To be used as a logic output, a port configured in this manner must have an external pullup, typically a resistor tied to VDD. The pulldown for this mode is the same as for the quasi-bidirectional mode.

The open drain port configuration is shown in Figure 4-2.

An open drain port pin has a Schmitt-triggered input that also has a glitch suppression circuit (please refer to the P89LPC906/ 907/908 datasheet, AC Characteristics for glitch filter specifications).

port latch data

input data

port

pin

glitch rejection

Figure 4-2: Open Drain Output

2003 Dec 8

36

Image 36

Contents User Manual Table of Contents Brownout Detection Power-On Detection Power Reduction Modes Power-On reset code execution103 List of Figures List of Figures PIN Configurations P89LPC906Logic Symbols Product ComparisonBlock Diagram P89LPC906 KB Code FlashCPU Oscillator DividerBlock Diagram P89LPC907 UartByte Data RAM ClockBlock Diagram P89LPC908 Data RAM PortPIN Descriptions P89LPC906 PIN Descriptions P89LPC907 P1.0TxD P1.2PIN Descriptions P89LPC908 Keyboard Input P1.0 P1.5P1.1 RxDSpecial function registers Special function registers table P89LPC906MSB 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 Memory Organization DataSFR CodeEnhanced CPU Clock DefinitionsCPU Clock Oscclk LOW Speed Oscillator Option P89LPC906Oscillator Option SELECTION- P89LPC906 Clock Output P89LPC906ON-CHIP RC Oscillator Option Watchdog Oscillator OptionCPU Clock Cclk Wakeup Delay BIT Symbol FunctionExternal Clock Input Option P89LPC906 CPU Clock Cclk Modification Divm RegisterLOW Power Select P89LPC906 High freqMed freq Low freqCPU Clocks Flag Bits Address Enable Bits Priority Ranking Interrupt Priority StructureSummary of Interrupts P89LPC906 Description Interrupt ArbitrationExternal Interrupt Inputs External Interrupt PIN Glitch SuppressionSummary of Interrupts P89LPC907,P89LPC908 Description TI & RIBopd EBO Rtcf Kbif Interrupts Port Configurations QUASI-BIDIRECTIONAL Output ConfigurationNumber of I/O Pins Available Clock Source Reset Option RSTOpen Drain Output Configuration Port latch dataINPUT-ONLY Configuration PUSH-PULL Output ConfigurationPort 0 Analog Functions Strong Port latch data Port pin Input data Glitch rejectionPort Output Configuration P89LPC906 Port Output Configuration P89LPC907Port Output Configuration P89LPC908 Ports Ports Tmod TMOD.7TMOD.6 TMOD.3Overflows. Mode ModeTamod P89LPC907 TAMOD.7-1Tcon Pclk T0C/T = Overflow TLn THn TFn Interrupt T0 PinT0C/T = Overflow THn TFnTimer Overflow Toggle Output P89LPC907 Pclk TL0TR0 ENT0 Pclk TH0 Timers 0 REAL-TIME Clock Source FOSC2 FOSC1 FOSC0 RTCS10 UCFG1.2 UCFG1.1 UCFG1.0 Cclk Frequency RTC Clock FrequencyXclk Divm CclkRC Oscillator/DIVM WDT Oscillator/DIVMUndefined External clock/DIVMReset 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 Uart ModesSFR Space Baud Rate Generator and SelectionUpdating the BRGR1 and BRGR0 Sfrs SFR Locations for UARTsFraming Error Break DetectBrgcon Scon More about Uart Mode SstatSerial Port Mode 0 Double Buffering Must Be Disabled Framing Error and RI in Modes 2 and 3 with SM2 = FE and RI when SM2 = 1 in Modes 2More about Uart Modes 2 PCON.6 RB8 SMOD0Double Buffering Double Buffering in Different Modes9TH BIT BIT 8 in Double Buffering Modes 1, 2 Transmission with and without Double BufferingMultiprocessor Communications Automatic Address RecognitionUart Uart POWER-ON Reset Code Execution Block Diagram of ResetRstsrc Comparator Configuration Comparator and Power Reduction Modes Internal Reference VoltageComparator Interrupt CIN1A CO1 CMP1 CmprefComparator Configuration Example Analog Comparators Kbpatn KbconKbmask Watchdog timer configuration Watchdog FunctionWdte Wdse Function Feed Sequence Wdcon P89LPC906/907/908 Watchdog Timeout Values PRE2-PRE0Watchdog Timer in Timer Mode Prescaler Reset PclkWatchdog Control registerPower Down Operation Watchdog Clock SourcePrescaler CLKWatchdog Timer Watchdog Timer Software Reset Dual Data PointersAUXR1 MOVCA, @A+DPTR Move code byte relative to Dptr to the accumulatorMOVXA, @DPTR MOVX@DPTR, aFeatures Using Flash AS Data StorageGeneral Description Introduction to IAP-LITEFlash Program Memory Fmcon Accessing Additional Flash Elements Assembly language routine to erase/program all or part of aERASE-PROGRAMMING Additional Flash Elements Reading Additional Flash ElementsUCFG1 Fmadrl Conf User Configuration Bytes UCFG1P89LPC906 User Security Bytes SECxAddress xxxxh Unprogrammed value 00hBootvec BootstatArithmetic LogicalMnemonic Description Bytes Cycles Hex Code Data TransferBoolean BranchingReti B8-BFD8-DF Miscellaneous2003 Dec Initial release 104 Index Dual Data Pointers Port 0 12, 13 SFR 109 P89LPC906/907/908