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ClockCard Technical Specifications

PCI version

ISA version
 

PCI CARD
Setup
  • Address: plug and play compatible
  • Interrupt: None required
Bus
  • PCI bus 
Clock
  • Power control circuitry supports system power on from date/time alarm or key closure
  • Century register, Y2K–compliant
  • Date alarm register
  • Compatible with existing BIOS
  • Timekeeping algorithm includes leap year compensation valid up to 2100
Oscillator
  • Temperature-Compensated 32 KHz Crystal Oscillator
  • Meets the 1998 European network server recommendation for real-time clock (RTC) accuracy.
  • The steady 32.768 kHz output of the DS32KHz maintains the accuracy of the real-time clock within 2 PPM (1 minute) per year from 0 to 40C
  • Temperature Stability: < 2 PPM 0 - 40 C
  • Calibration: < 1 PPM @ 23 C (room temperature)
  • Aging: < 1 PPM
Battery
  • Includes replaceable lithium  battery for backup power.
  • Battery is lithium thionyl chloride, high drain capability 3.6V AA-sized cell. It has a 2.25Ah rated capacity. Battery will operate reliably up to 85C, and has a self discharge rate of less than 0.5% a year. Has a stainless steel container and hermetic glass-to-metal sealing. Widely used in  military, aerospace and technical service.
  • Battery Life: approximately 5 years without host computer power.
     
Dimensions
  • PCI card - 4.5" l x 4.0" h

 

ISA CARD
Setup
  • Address: User selectable with jumpers (6 possible DMA addresses)
  • Interrupt: None required
Bus
  • ISA bus, short (8 bit) slot. 
Clock Resolution
  • 0.01 seconds
Oscillator
  • Temperature Stability: < 5 PPM 0 - 50 C
  • Calibration: < 1 PPM @ 23 C (room temperature)
  • Aging: < 1 PPM
Power Requirements
  • 35 mA @ 5Vdc
Battery
  • Includes integral lithium  battery for backup power
  • Battery Life: approximately 5 years without host computer power.
Dimensions
  • half height ISA card - 4.8" l x 3.0" h

 

 

Temperature Compensation in the PCI version Oscillator

The ClockCard PCI includes a temperature compensated 32KHz oscillator DS32KHz is a highly  accurate replacement for standard 32.768-kHz crystals commonly used in real time clocks (RTC).  

The oscillator provides accuracy at 1 minute per year (2 parts per million) in operation from 0 to 40C, making it one of the industry's most accurate 32.768-kHz oscillators.

Accurate timekeeping is very important in network servers that have lots of PCs connected to them, With timed-access communications, there's a need for accuracy and synchronization. When a great deal of information is coming in and every system time-stamps it differently, more accurate references are needed.

Nobody puts an RTC in a system and expects it to keep inaccurate time. Most people don't understand why a $9.95 watch can keep accurate time but a $3,000 PC and a $20,000 server can't. Watches keep good time because they're trimmed to operate at body temperature. The inside temperatures of most computer chassis vary more than few degrees.

Most other Real time clocks are calibrated to keep time accurately at 25C. If internal computer temperatures are hotter or colder, the clocks run more slowly. Accuracy over temperature typically depends on crystal characteristics, and higher accuracy over temperature is achievable by trimming the crystal.  Accuracy needs to be repeatable day in and day out Timekeeping in computers that operate at elevated temperatures can be significantly inaccurate. The effect of temperature on accuracy is cumulative; it is not self-correcting.

Inside the ClockCard PCI oscillator package are a quartz crystal and a temperature-compensation IC. The compensation IC employs low current oscillator technology and  thermal-sensing technology. It is this temperature compensation that gives the overall precision of the PCI ClockCard in the 2 PPM range.

ClockCard PCI meets the precision timekeeping requirements of large computer networks, financial transaction processing applications, and timed-access communications.
 

Oscillator Error, ISA version

The precision of the ClockCard is entirely dependent on the quality of the oscillator circuit. There are three sources of error in the oscillator:  (1) calibration error, (2) temperature stability, and (3) aging.  Understanding these will allow you to estimate the precision of the ClockCard in your application.

Calibration error:  The ClockCard oscillator is calibrated at the factory to within 1 PPM part per million) of its specified frequency at room temperature (23 C or 73 F).

Temperature Stability:  The frequency of oscillation of crystal oscillators is highly dependent on temperature. The oscillator used in the ClockCard has an extremely low temperature dependency of 5 PPM from 0 C to 50 C (32 F to 122 F).  Since the oscillator is calibrated to 1 PPM at room temperature (23 C), it will only exhibit 1 PPM error if its environment is held to this temperature. The worst case condition is if the temperature of the ClockCard is held at one of the extremes, 0 or 50 C. At these points, there will be an error of 5 PPM. If the temperature variation covers a smaller span, less error will be exhibited.

Aging:  All crystal oscillators have an aging characteristic. The crystal used in the ClockCard uses the coldweld manufacturing technique, which exhibits the lowest aging characteristic of 1 PPM per year.  In practice, this aging rate improves significantly with time, but for practical purposes the value of 1 PPM is adequate.

To estimate the error in your application, sum the error from the three sources above. This estimate can be used to determine how frequently the time should be updated using Beagle Software's ClockWatch or another method.

Parts Per Million (PPM) Terminology

The unit PPM (parts per million) provides a number similar to error expressed with percentages, but reduces the number of decimal places required.  For example, 0.001% converts to 0.00001which is equivalent to 10 PPM.  Using the PPM notation makes it easier to deal with very small deviations.

The PPM terminology is also useful for calculating ClockCard error in terms of seconds per month. Since an average month has approximately 2.63 million seconds, if the ClockCard error was 2 PPM, then total error for the month would be 2 x 2.63 = 5.26 seconds.

ClockCard Product Guide
ClockCard Product List
ClockCard Main Page

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Copyright 2004 Beagle Software. All rights reserved
Last reviewed September 13, 2004