P104-WDG-CSMA Watchdog Timer and Status Monitor

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  • PC/104 Plus Watchdog Timer card with software selectable timeout from 4 µsec
  • Watchdog open collector reset outputs
  • Temperature sensor with calibration pot
  • Temperature monitor / alarm
  • Temperature measurement with 8-bit A/D
  • Fan status and speed control
  • PCI/104 power monitor / limit alarm interrupt
  • Opto-isolated input to trigger reset
  • General purpose opto-isolated input
  • Two isolated outputs, current limited
  • TTL reset pushbutton input
  • Two general purpose 8-bit A/D inputs
  • External fused 5V and 12V power
  • Light sensor for enclosure security
  • Supported in DOS, Windows, Linux
  • PC/104 bus pass through connector
Last updated on November 2, 2023, 6:27 pm


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PC/104 Plus Watchdog Timer Status Monitor

This multifunction card contains a watchdog timer used to monitor the operation of your application program and operating system to initiate a system reset in case of a lockup. It can also monitor and control a variety of system hardware parameters. Three models with increasing features are available.


Economy version which includes the full programmable watchdog timer with open collector outputs that can reset the computer. This requires your application program to have embedded watchdog software code that communicates a prompt to the timer. If this prompt is missed, a hard computer reset is initiated after the user programmed watchdog timer period has been reached. This is valuable where the lock up of the application is due to being in a software loop where some hardware watchdogs cannot detect.


The Computer Status Monitor (CSM) version includes features in the economy model and adds capability to monitor the health and control various computer functions. The PCI-Bus 5V and ±12V are monitored and if any voltage varies by more than 6%, an interrupt can be generated. The temperature monitor compares an on-board temperature sensor output to a preset reference (approximately 50°C). A status register indicates normal or high temperature and can also generate an interrupt. The temperature measurement circuit uses an on-board 8-bit A/D as the digitizer. This model also provides one general-purpose opto-isolated input. Two digital isolated outputs are provided to control/switch external events in response to CSM conditions. In parallel to these two isolated outputs are two non-isolated digital outputs that can sink/source up to 15mA and can drive LEDs to indicate the switched event of the isolated outputs or simply output to another device the same digital state. A fused 5V external power pin is provided to bias external LEDs when used with non-isolated digital outputs. A push button reset input is also provided to directly initiate a system reset.


This advanced version builds on the P104-WDG-CSM but has all available features populated. Two undedicated 8-bit A/D (Analog Inputs) with a 0-5V range can be used to measure critical system parameters such as battery voltage or humidity. The fan speed control can be used in conjunction with the temperature monitor to maintain internal temperatures in the enclosure by the control of fan speed. The duty cycle of fan power (+12V) is pulse-width modulated to speed up the fan when temperature increases. If no current is detected or the duty cycle reaches 100%, an interrupt occurs. Another advanced feature is a Security Light Sensor used to detect if a darkened interior of the enclosure is opened letting in light. An external remote reset through a dedicated opto-isolated digital input is provided that can allow any transition between 3-18V to reset the computer. This reset could be triggered remotely from an RS-232 signal transition if available. Finally, additional fused 5V and 12V pins are provided on I/O connector for powering external circuitry or devices.


An additional option of a PCI-104 version allows this board to be added to the top of a PCI-104 express stack without mechanical interference. The P104-WDG-CSM is designed for use in both industrial/commercial and optionally military environments of 0 to +70°C and -40 to +85°C, respectively. Programmable array logic is available on this card and many possibilities exist for special modifications to suit unique requirements.


Sample programs and source code in “C” and Pascal for DOS, and Visual Basic, Delphi and Visual C++ for Windows on CD ships with the hardware you order. Also incorporated for the P104-WDG-CSM is support for use in most operating systems and includes a DOS, Linux, and Windows XP -> 10, both 32 & 64 bit compatible software package. Third party support for watchdog timer consists of a standard dll interface usable from most popular application programs. Linux support consists of installation files and basic samples for programming from user level via an open source kernel driver.


  • PCI-104 only
  • Extended Temperature


Ribbon Cables, Screw Terminal Panels and Splice Connectors are standard available accessories. Depending on your application you may need something special so give us a call and one of our application specialists will work with you to find the best possible solution.


Data Sheets



Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.

Watchdog Timer

  • Time-out: Software selectable from 4 µsec to 2060 sec
  • Clock: 2.08333 MHz, derived from computer clock (33 MHz ÷ 16)
  • Address: 8-Bit I/O Mapped

Status Register

  • Voltages: If +5V, +12V or -12V varies by more than ±6%
  • Temp Alarm: IRQ and status register indication if temperature is above 122°F (50°C)
  • Temp Digitizer: 8-bit ADC, LSB = 0.7°F (.39° C)
  • Fan Speed: IRQ and Status register indication if speed is too high or two low

Digital Outputs

  • Isolated: Two, 5V through a 330 ohm resistor
  • Non-Isolated: Two, controlled with isolated outputs to drive LED (up to 15mA sink/source)
  • Reset Outputs: One active low open collector, One active high with 1K pull-up
  • Fan Pulse Width 120 nsec. min., 31 msec. max.

Digital Inputs

  • Isolated: Two, limited through a 330 ohm resistor – one dedicated RESET input, one general purpose available


  • Operating Temp: 0 to +70°C (optional -40 to +85°C)
  • Storage Temp: -50°C to +120°C
  • Humidity: 10% to 90% RH, non-condensing
  • Power: +5VDC @ 125mA typical
ModelDescriptionPrice (USD)

PC/104 Plus Watchdog Timer Status Monitor Economy Version


PC/104 Plus Watchdog Timer Status Monitor Standard Version


PC/104 Plus Watchdog Timer Status Monitor Advanced Version


ORDERING GUIDE / P1 Connector Configurations

  • 4-pin right-angle 2×2 header (9-12)
  • 4-pin above plus;
  • 6-pin right-angle 2×3 header (1-6)
  • 2-pin right-angle 1×2 header (15-16)
  • 10-pin rt-angle 2×5 header (25-34)
  • 40-pin right-angle shrouded 2×20 header
  • JP2, Reset Isolated Input, 2-pin right-angle header with 0.1″ spacing


Ribbon Cables, Screw Terminal Panels and Splice Connectors are standard available accessories. Depending on your application you may need something special so give us a call and one of our application specialists will work with you to find the best possible solution