Information MFAM 1 PPS signal input, 10 MHz reference input and synchronization

The 1PPS pulse phase locks and synchronizes the sample interval to be in lock step with the GPS.  Thus once locked there will always be 1000 samples per second, with the sample beginning time precisely lined up with the 1 PPS edge.
 
The 10 MHz input is for a different function.  This input phase locks the 40 MHz master reference oscillator to the incoming 10 MHz, which is usually a GPS disciplined reference oscillator or atomic clock (in other words exactly 10 MHz).  This phase locks the 40 MHz reference oscillator to exactly 40 MHz.  The 40 MHz oscillator is the time base reference for calculating the Larmor frequency, and therefor the magnetic field value.
 
Even though the 40MHz oscillator is really good even without the 10 MHz input, there is some drift in the 40 MHz over time (mostly thermal drift and some aging).  For some applications where they need to measure very low frequency and low amplitude changes in the magnetic field the 10 MHz input will allow drifts in the reference oscillator to be removed.  Without that it would be impossible to distinguish between reference oscillator drifts and low frequency low amplitude changes in the magnetic field.

The connector for the 10 MHz input is SMB RF connector from Molex.

If you must simulate the 1 PPS signal in a GPS denied environment, please be aware of certain requirements of the 1 PPS signal.

1. The lock range for the 1 PPS input pulse is very narrow. The simulated 1 PPS signal must be within 100 ppm of an exact 1 Hz PPS signal (100us).

2. Timing jitter must be small (less than 0.5 ppm, 0.5us) too. If you are setting a GPIO pin on a microcontroller, there may be some concern about timing jitter due to interrupt latency or other processor tasks delaying the I/O pin toggle.  Any rectangular waveform should work but the leading edge must be very close to 1 Hertz.  It is the positive edge that specifies the 1 second rollover.