Philips P89LPC901, P89LPC903, P89LPC902 user manual Feed Sequence

Page 84

Philips Semiconductors

 

 

 

 

 

 

 

 

User’s Manual - Preliminary -

WATCHDOG TIMER

 

 

 

 

 

P89LPC901/902/903

Watchdog

 

 

 

 

 

 

 

 

 

Oscillator

÷32

÷2

÷2

 

÷2

÷2

÷2

÷2

÷2

 

PCLK

 

 

 

 

 

 

 

 

 

 

 

÷32

÷64

÷128

÷256

÷512

÷1024

÷2048

 

÷4096

 

WDCLK after a

 

 

 

 

 

 

 

 

 

 

watchdog feed

 

 

 

 

 

 

 

 

 

 

sequence

 

 

 

 

 

 

 

 

TO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WATCHDOG

 

 

000

 

 

 

 

 

 

 

DOWN

 

 

 

 

 

 

 

 

 

COUNTER

 

 

001

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(after one

 

 

010

 

 

 

 

 

 

 

PRE2

 

 

 

 

 

 

 

 

prescaler

 

011

 

 

 

 

 

 

 

 

DECODE

 

 

 

 

 

 

 

count delay

PRE1

100

 

 

 

 

 

 

 

 

 

101

 

 

 

 

 

 

 

 

PRE0

 

110

 

 

 

 

 

 

 

 

 

111

 

 

 

 

 

 

 

 

Figure 12-1: Watchdog Prescaler

Feed Sequence

The watchdog timer control register and the 8-bit down counter (Figure 12-3) are not directly loaded by the user. The user writes to the WDCON and the WDL SFRs. At the end of a feed sequence, the values in the WDCON and WDL SFRs are loaded to the control register and the 8-bit down counter. Before the feed sequence, any new values written to these two SFRs will not take effect. To avoid a watchdog reset, the watchdog timer needs to be fed (via a special sequence of software action called the feed sequence) prior to reaching an underflow.

To feed the watchdog, two write instructions must be sequentially executed successfully. Between the two write instructions, SFR reads are allowed, but writes are not allowed. The instructions should move A5H to the WFEED1 register and then 5AH to the WFEED2 register. An incorrect feed sequence will cause an immediate watchdog reset. The program sequence to feed the watchdog timer is as follows:

CLR

EA

; disable interrupt

MOV

WFEED1,#0A5h

; do watchdog feed part 1

MOV

WFEED2,#05Ah

; do watchdog feed part 2

SETB

EA

; enable interrupt

This sequence assumes that the P89LPC901/902/903 interrupt system is enabled and there is a possibility of an interrupt request occuring during the feed sequence. If an interrupt was allowed to be serviced and the service routine contained any SFR writes, it would trigger a watchdog reset. If it is known that no interrupt could occur during the feed sequence, the instructions to disable and re-enable interrupts may be removed.

In watchdog mode (WDTE = 1), writing the WDCON register must be IMMEDIATELY followed by a feed sequence to load the WDL to the 8-bit down counter, and the WDCON to the shadow register. If writing to the WDCON register is not immediately followed by the feed sequence, a watchdog reset will occur.

For example: setting WDRUN = 1:

MOV

ACC,WDCON

; get WDCON

SETB

ACC.2

; set WD_RUN=1

MOV

WDL,#0FFh

; New count to be loaded to 8-bit down counter

CLR

EA

; disable interrupt

MOV

WDCON,ACC

; write back to WDCON (after the watchdog is enabled, a feed must occur

 

 

; immediately)

2003 Dec 8

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Contents User Manual Philips SemiconductorsTable of Contents Power Monitoring Functions 103 P89LPC901/902/903 List of Figures Pin Configurations P89LPC902Logic Symbols Product comparisonBlock Diagram P89LPC901 CPUBlock Diagram P89LPC902 High Performance Accelerated 2-clock 80C51 CPUBlock Diagram P89LPC903 UartMnemonic PIN no Type Name and Function CIN1AKBI4 KBI5P3.1 XTAL1CMP2 KBI0CIN2A KBI2P1.0 TxDP1.1 RxDSpecial Function Registers Special Function Registers Table P89LPC901Bit Functions and Addresses Hex Special Function Registers Table P89LPC902 CMP1 Cmpref CIN1A KB2 KB0 KB6 KB5 KB4 A7H PRE2 PRE1 PRE0 Wdrun Wdtof Special Function Registers Table P89LPC903 F7H Psth PCH Pkbih TRIM.5 TRIM.4 TRIM.3 TRIM.2 TRIM.1 TRIM.0 WDCON# P89LPC901/902/903 Memory Organization DataSFR CodeGeneral Description Enhanced CPU Clock DefinitionsCPU Clock Oscclk Low Speed Oscillator Option P89LPC901Oscillator Option Selection- P89LPC901 Clock Output P89LPC901On-Chip RC oscillator Option BIT Symbol Function Watchdog Oscillator OptionExternal Clock Input Option P89LPC901 TrimHigh freq Med freqLow freq DivmAtchdog CPU Clock Cclk Wakeup Delay CPU Clock Cclk Modification Divm RegisterL K O sc illa to rP89LPC901/902/903 Low Power Select P89LPC901 P89LPC901/902/903 Interrupt Priority Structure Flag Bits Address Enable Bits Priority Ranking Summary of Interrupts P89LPC901 DescriptionInterrupt Arbitration Summary of Interrupts P89LPC902 DescriptionP89LPC901/902/903 External Interrupt Inputs External Interrupt Pin Glitch SuppressionTF1 ET1 TI & RI/RI ES/ESR Port Configurations Quasi-Bidirectional Output ConfigurationNumber of I/O Pins Available Clock Source Reset Option RSTOpen Drain Output Configuration Quasi-Bidirectional OutputP89LPC901/902/903 Input-Only Configuration Push-Pull Output ConfigurationPort 0 Analog Functions Additional Port Features Port Output Configuration P89LPC901Port Output Configuration P89LPC902 Port Output Configuration P89LPC903Ports Ports Tmod TMOD.7TMOD.6 TMOD.3Mode Tamod P89LPC901TAMOD.7-1 TAMOD.0P89LPC901/902/903 Mode Mode 6 P89LPC901Tcon Timer/Counter 0 or 1 in Mode 0 13-bit counter PclkTimer Overflow toggle output P89LPC901 Pclk TL0TR0 ENT0 Pclk TH0 Timers 0 Real-time clock/system timer Block Diagram Real-time Clock SourceReal-time Clock/System Timer Clock Source P89LPC901 FOSC2 FOSC1 FOSC0 RTCS10UCFG1.2 UCFG1.1 UCFG1.0 Cclk Frequency RTC Clock Frequency XclkReset Sources Affecting the Real-time Clock Real-time Clock/System Timer Clock Source P89LPC902/903Changing RTCS1-0 Real-time Clock Interrupt/Wake UpRtccon Brownout Detection Power-On Detection Brownout OptionsP89LPC901/902/903 Power Reduction Modes Power Reduction ModesPcon Pcona Power Monitoring Functions Uart P89LPC903 P89LPC901/902/903 SFR 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 2P89LPC901/902/903 More About Uart Modes 2 PCON.6 RB8 SMOD0P89LPC901/902/903 Double 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 P89LPC903 Uart P89LPC903 Power-On reset code execution Block Diagram of ResetRstsrc Comparator Configuration CMPnComparator Input and Output Connections P89LPC901 Internal Reference Voltage Comparator InterruptCmpref Comparator and Power Reduction Modes Comparator Configuration ExampleKbpatn KBPATN.5,4Kbcon KbmaskKBMASK.7 KBMASK.6KBMASK.3 KBMASK.2Keypad Interrupt KBI Watchdog timer configuration Watchdog FunctionWdte Wdse Function Feed Sequence Wdcon P89LPC901/902/903 Watchdog Timeout Values Prescaler Reset PclkWDCONA7H P89LPC901/902/903 Watchdog Timer in Timer Mode Power down operationWatchdog Clock Source PrescalerWatchdog Timer Watchdog Timer Watchdog Timer Software Reset Dual Data PointersAUXR1 MOVCA, @A+DPTR MOVXA, @DPTRMOVX@DPTR, a Features Using Flash as data storageGeneral description Introduction to IAP-LiteFlash Program Memory Fmcon Accessing additional flash elements C-language routine to erase/program all or part of aErase-programming additional flash elements Reading additional flash elementsUCFG1 Fmadrl User Configuration Bytes C-language routine to read a flash elementUCFG1 P89LPC901User Security Bytes SECxP89LPC901/902/903 Boot Vector Boot StatusBootvec BootstatArithmetic LogicalMnemonic Description Bytes Cycles Hex Code Data TransferBoolean BranchingReti B8-BFD8-DF MiscellaneousRevision History 108 Index Dual Data Pointers Port 0 12, 14 SFR 113 P89LPC901/902/903

P89LPC903, P89LPC902, P89LPC901 specifications

The Philips P89LPC901, P89LPC902, and P89LPC903 are a series of 8-bit microcontrollers designed for embedded system applications. These models, which belong to the LPC900 series, are notable for their affordability and versatility, making them an attractive choice for both hobbyists and professional developers.

One of the core features of the P89LPC901, P89LPC902, and P89LPC903 microcontrollers is their powerful 8-bit architecture. Operating at clock speeds up to 20 MHz, they deliver efficient performance suited for a range of tasks. Each model includes a comprehensive instruction set that supports various data manipulation and arithmetic functions, enabling extensive programming capabilities.

These microcontrollers come with built-in memory, with configurations that vary among the three models. The P89LPC901 typically features 4 KB of Flash memory and 256 bytes of RAM, while the P89LPC902 and P89LPC903 offer enhanced memory options. This Flash memory allows for reprogrammability, making it easier to update and modify applications as needed.

Another significant characteristic of the LPC900 series is their integrated peripherals. These models are equipped with a variety of I/O ports, allowing for easy interfacing with other devices and components. The P89LPC901 supports up to 32 I/O pins, while the P89LPC902 and P89LPC903 provide additional features such as analog-to-digital converters (ADCs), timers, and serial communication interfaces. This broad range of peripherals empowers developers to design complex applications without needing extra hardware.

Power consumption is also a key consideration for microcontroller applications. The P89LPC901, P89LPC902, and P89LPC903 are designed with low power consumption in mind, making them ideal for battery-operated devices and energy-efficient projects. They can operate in various power modes, allowing for greater flexibility in deployment.

In terms of technology, these microcontrollers utilize advanced CMOS technology, ensuring high reliability and durability. Their design offers a robust solution for numerous applications, including consumer electronics, industrial controls, and automation systems.

In summary, the Philips P89LPC901, P89LPC902, and P89LPC903 microcontrollers present an attractive combination of performance, integrated peripherals, low power consumption, and versatility. Their features cater to a wide array of applications, keeping them relevant in a rapidly evolving technology landscape. For hobbyists and professionals alike, these microcontrollers represent a reliable foundation for embedded system development.
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