The IO821 I/O module - with optional GNSS (GPS/GLONASS) receiver – provides precision timing and synchronization for real-time applications and includes both input and output interfaces to IRIG and 1PPS. The precision timing reference uses an onboard oscillator with 5ns resolution that is phase-locked to an external timing reference input.
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 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.
Features
1PPS
- Input and output 1PPS interfaces
- Output accuracy: UTC ± 15ns for stationary conditions (IO821-GNSS only) and UTC ± 50ns for other conditions (locked to GPS or 1PPS source).
- TCXO holdover accuracy: 12 μs after 4 hours and 450 μs after 24 hours (IO821)
- OCXO holdover accuracy: 3 μs after 4 hours and 100 μs after 24 hours (IO821-GNSS)
- User-selectable lead time for the 1PPS output to delay model execution start.
IRIG
- Inputs and outputs for both IRIG DCLS and IRIG AM
- The IRIG inputs accept IRIG (formats A, B, G), NASA36 and IEEE 1344
- The IRIG outputs accept IRIG (formats A, B, E, G), NASA36 and IEEE 1344
- User-selectable lead time to delay IRIG AM output
Crystal oscillator
- Capable of 5ns resolution
- Disciplined by and phased-locked to external timing input
- TCXO oscillator with IO821 variant and OCXO oscillator with IO821-GNSS variant.
- 10 MHz oscillator output
GNSS receiver (IO821-GNSS only)
- 72-channel receiver with concurrent dual-constellation reception
- Supports GPS, QZSS, GLONASS and BeiDou.
- Initial acquisition time of 26 s for cold start (GPS & GLONASS)
Additional Features
- 2 Edge Detection Inputs allowing a precise time stamping of external events
- 2 Hardware Trigger Outputs to control external Hardware
Variants
| I/O module |
Timing Sources
|
Timing Outputs
|
Crystal Oscillator
|
GNSS receiver
|
|
IO821
|
1PPS, IRIG |
1PPS, IRIG, 10MHz
|
TCXO |
No |
|
IO821-GNSS
|
1PPS, IRIG, GNSS
|
1PPS, IRIG, 10MHz
|
OCXO
|
Yes |