Trimble Outdoors SK8 - Manual (Page 41)

Lassen-SK8 Embedded GPS Module 2-5
Hardware Integration
2.5 Pulse Per Second
A ten microsecond wide, CMOS compatible TTL level pulse is available on pin 6 of the J4
I/O connector. This pulse is issued once per second with the rising edge of the pulse
synchronized with UTC. The pulse will be shaped by the distributed impedance of the
attached signal line and input circuit. The rising edge is typically less than 20 nSec. The
falling edge should not be used.
The timing accuracy is ± 100 nanosecond (1 Σ ) and is available only when valid position
fixes are being reported. Repeatability checks of 10 sets of 100 one second samples taken
over a period of 20 minutes showed an average variation of approximately 100
nanoseconds (not allowing for SA).
2.6 Mounting
The Lassen-SK8 provides four 0.125 inch mounting holes that will accept 3/16 inch round
or hex standoffs with 3/8 inch height, and #4 or M3 mounting screws. Space constrained
environments may require a different stand-off. Refer to the mechanical outline drawing
in Appendix F for dimensions and clearances.
2.7 RF Shield
An optional RF shield is available for production versions of the standard temperature
Lassen-SK8 module. The production versions of the Lassen-SK8 do not have a socketed
EPROM. This RF shield protects the GPS module from interference with other electronics
and also makes the module compliant with the CE emission specification. The RF shield is
not compatible with the socketed board provided in the Starter Kit nor with the extended
temperature board that has a TCXO oscillator.
*
Note – Many installations do not require the optional shield. The Lassen-SK8 is designed
to be immune to most interference.