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Precision-Timing I/O Module with IRIG and 1PPS Interfaces, Optional GNSS, and Simulink® Driver Blocks

The IO821 I/O module (with an optional GNSS (GPS/GLONASS) receiver) provides precision timing and synchronization for real-time applications, and includes both IRIG and 1PPS input and output interfaces. The precision timing reference uses a 5 ns-resolution onboard oscillator that is phase-locked to an external timing reference input. Simulink driver blocks are also provided.

This I/O module supports multiple timing inputs and, when the current timing input is lost, it switches automatically to the next lower-priority input. Furthermore, the crystal oscillator provides uninterrupted precision timing even when all external sources become unavailable (referred to as holdover). For applications where accuracy during holdover is essential, an oven-controlled crystal oscillator (OCXO) is optionally available.

The IO821 I/O module is fully compatible with the Simulink Real-Time™ workflow. It can be used to generate an interrupt which triggers the Simulink model execution at very precise intervals. In addition, it can supply precision timing references to synchronize external hardware.

 Key Features

  • 1PPS input and output interfaces
  • Inputs and outputs for both IRIG AM and IRIG DCLS
  • Crystal oscillator capable of 5 ns resolution
  • Optional GNSS receiver supporting GPS, QZSS, GLONASS and BeiDou


Form factor PMC
Power requirements 7 W @ 5 V typical
2.3 W @ 3.3 V typical
2.4 W @ +12 V typical
2.4 W @ -12 V typical
Electrical interface PCI D32, 33/66 MHz, specification 2.3
Connectors 25-pin micro-miniature D-sub plug
Includes adapter cable with:
1) DB-9 female: IRIG DCLS Input
2) BNC female: IRIG AM input
3) BNC female: IRIG AM output
4) BNC female: 1PPS input
5) BNC connector: 1PPS output
Operating temperature -40°C to +80°C
Relative humidity 95% at 60 °C for 5 cycles of 48 hours/cycle
Certification RoHS, CE, FCC Class A
Crystal oscillator
Resolution 5 ns
Phase-locked Disciplined by and phase-locked to external timing input
Type TCXO (default)
OCXO (-GNSS option) for extended holdover accuracy
Accuracy 1x10-11s (TCXO)
5x10-12s (OCXO)
Medium-term stability 1x10-8 s / day for TCXO
2x10-9 s for OCXO (-GNSS option)
(both without CPS after 2 weeks of GNSS lock)
Output 10-MHz sine wave (50 Ohm output impedance)
Timing inputs
External 1PPS input 1 Hz pulse, rising edge active
IRIG AM Input Accepts IRIG (formats A, B, G), NASA36 and IEEE 1344 pulse width codes
IRIG DCLS Input Accepts IRIG (A, B, G formats), NASA36, IEEE 1344 pulse width codes
Timing outputs
1PPS 1 Hz pulse with 200 ms pulse width
IRIG AM Output Output formats A, B, E (100 Hz, 1 kHz), G; NASA36; IEEE 1344
IRIG DCLS Output Output formats A, B, E (100 Hz, 1 kHz), G; NASA36; IEEE 1344
GNSS receiver
GNSS support GPS, QZSS, GLONASS and BeiDou
Acquisition times 26 s for cold start (GPS & GLONASS)

Item ID Product Name Components
2A821X IO821
  • 1x IO821 I/O module
  • Dedicated cables with BNC and D-Sub connectors
  • Driver block library for Simulink Real-Time™
  • Comprehensive documentation and Simulink example models
  • Installation into the real-time target machine
Optional Accessories    
2B821X IO821-GNSS 1x IO821 I/O module with GNSS input

Key to X in Item ID
Please replace the X with the code number of the specific target machine into which this I/O module shall be installed:

  • 5 = Mobile real-time target machine
  • 6 = Performance real-time target machine
  • 8 = Baseline real-time target machine

Pricing information
We don't publish pricing information on our website. Upon request by e-mail or phone we can provide a complete price list covering our entire product portfolio in various currencies. We recommend that you get in touch with us to discuss your specific needs. We can then quickly provide you with a tailored quotation including technical and pricing information.


Included in the Delivery

  • I/O module installed into real-time target machine
  • Cable for loopback testing
  • Simulink driver blocks
  • Test models
  • Comprehensive documentation

Common Applications

Supported target machines

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