Remote Technologies RPC-320 manual Watchdog Timer, External Reset

Page 43

WATCHDOG TIMER

SECTION 11

DESCRIPTION

The watchdog timer is used to reset the RPC -320 if the program or CPU "crashes" . The time r is built into the 80C320 CP U. Timed access requirem ents built into the CPU make it high ly unlikely an er rant pr ocessor would cancel a watchdog timer .

The watchdog should not be used in loops which do not end quickly or ar e of indetermina te duration unless a WDOG command is included. An example of an indeterminate loop is one that waits for a port condition to change.

The timer is set by executing a WDOG n command. n is 0, 1, or 2. 0 turns off the timer. 1 sets the watch dog time to 380 ms while 2 sets it to 2.8 seconds. Executing WDO G by itself resets the timer. WD OG must be executed pe riodically to p revent a reset.

When the watchdog times out, a softwar e reset is

perfor med. The effe ct is lines at J3 do not ch ange as in a power-up or har dware reset. Lines at P6, display, and keypad port ar e reset to power -up conditions.

EXTERNAL RESET

The card is reset externally by mom entarily shorting W10[1- 2]. R eset is also achiev ed by shor ting W10-2 to ground . Maintain this short for at least 10 ms . The card will then reset for abo ut 350 ms.

Page 11-1 RPC-320

Image 43

Contents Trademarks REVRevision Table of Contents Sect ION 13 Multi Mode Counter Description Sect ION 11 Watchdog Timer DescriptionExternal Reset Interrupt CharacteristicsSoftware Revision History Manual Organization OverviewSection DescriptionTechnical Support Symbols and Term inologySystem layout Overview SectionIntroduction Operating PrecautionsEquipment Uploading and Downloading Programs Using a PCUsing a Terminal First Time OperationEditing programs and program ming hints Troubleshooting Where to GO from HereW3 autorun jumper Saving ProgramsSaving a Program EpromChanging Eprom Size AutorunningPreventing Autorun Loading a ProgramBsave CommandsAlternate Eproms BloadCOM0 Serial Port Serial PortsCOM1 Serial Port RS-422/485 Operating Information Serial Ports SectionRS-422/485 Termination network Two wire RS-485 Accessing Serial BuffersMultidrop Network Disabling CONTROL-C Accessing COM0 and COM1Serial Port PIN OUT RXD CTS Changing Memory Battery BackupChecking the battery RAM MemoryStoring Variables in RAM Reserved MemoryBlock Data Transfer Assembly Language InterfaceDigital I/O Ports Digital and Opto PortsDigital Por t J3 Optically Isolated Input Digital I/O CommandsDigital Port P6 High Current Port L8High Current Output Interfacing Digital I/O to an opto-module rack Interfacing to switches and other devicesDigital I/ O prog ramm ing exam ple Ls e Width Modulation PWM Conne ctor pin ou t J3 Digital and Opto Ports SectionLine B Config LineCount LineDate Setting Date and TimeM E Section Writing to the Display Connecting DisplaysProgramming Example Display Types Display Connector PIN OUTProgram explanation Keypad PortKeypad Port PIN OUT J5 Overvoltage conditions Connecting Analog InputsAnalog Input InitializationExamples u sing CON FIG AIN Differential ModeAcquiring Analog Data Noise Notes Temperature MeasurementAnalog Input Section Measuring Higher Voltages Data logging on a timer tickAmplifiers Converting Analog MeasurementsMeasuring 4-20 mA current loops Calibration External Reset Watchdog TimerOptically Isolated Interrupt Interrupt CharacteristicsProgram Example Optically isolated and TTL interrup ts Gate ProgrammingGND LoadCOU NT0 Further Power Reduction Power ManagementProgram Examp le Power Management SectionTechnical Information Electrical SpecificationsBank Mechanical SpecificationsMemory and I/O Bank MAP Jumper Descriptions