This is a simple divide-by-10,000,000 using an 8-pin AVR, the ATtiny13. It can be used to lock the QRP Labs kits (Ultimate3S QRSS/WSPR Transmitter, VFO/Signal Generator, and ProgRock) to a 10MHz frequency reference.

The ATtiny13 is clocked at the 10MHz input frequency from the frequency reference. You may need a buffer amplifier here if the amplitude of the 10MHz Frequency reference is not enough. The leading edge (low-to-high transition) of the 1pps output is very accurate. The pulse width is approximately 100ms (0.1 seconds). There is also a sync signal input. A low-to-high transition on this input restarts the timers, so that it synchronises the 1pps output with the incoming pulse input. Connect it to ground if not used. 

Pin connections

Pin 1 (processor reset) connect to +5V
Pin 2 is the 10MHz input frequency
Pin 3 is the output 1pps, i.e. input divided by 10,000,000
Pin 4 (Gnd) connect to 0
Pin 6 is the sync signal. A low-to-high pulse here syncs the 1pps 
Pin 8 (Vcc) connect to +5V

Downloads

Hex file for installation on an ATtiny13
C source file

Installation

The hex file should be installed on the ATtiny13. There is no EEPROM file (.eep). The fuses need to be set for external clock and remove the divide-by-8 fuse setting.