SA.45s Chip-Scale Atomic Clock
SA.45s CSAC User Guide Revision D
25
3.4.3.4
1PPS Synchronization (S)
To synchronize the 1PPS output (pin 10) to an externally applied 1PPS synchronization input (pin 9),
connect the external 1PPS signal to pin 9 and send the
command. The rising edge of the 1PPS output
!S
will synchronize to within ±100 ns (approximately) of the next rising edge of the 1PPS input. If a valid
1PPS input does not appear at the 1PPS input within 3 seconds, the operation is aborted and an error is
returned.
Example (synchronize 1PPS):
Command:
!S[CRLF]
Unit response:
S[CRLF]
or:
E[CRLF]
The unit response (S or E) occurs after either successful synchronization or 3-second timeout. This
permits the host system to verify successful synchronization.
Note: The single-character is a shortcut for
.
S
!S[CRLF]
3.4.3.5
Set 1PPS Disciplining Time Constant (D)
The time constant for disciplining to an externally-supplied 1PPS reference source may be selected to
provide optimal performance in a given application (see
).
"The Art of Disciplining" (see page 35)
The time constant can range between 10 to 10000 seconds. The 1PPS disciplining time constant is set
with the
command. The format for setting the time constant is
!D
!DX[CRLF]
where X is the new time constant in seconds.
Example (set disciplining time constant to 80 seconds):
Command:
!D80[CRLF]
Response:
80[CRLF]
To query the current time constant setting, without modifying the value, use the command
!D?
Example (query current disciplining time constant):
Command:
!D?[CRLF]
Response:
80[CRLF]
Note: The single-character is a shortcut for
.
D
!D?[CRLF]
3.4.3.6
Set 1PPS Disciplining Cable Length Compensation (DC)
Cable length compensation can be applied to allow for known delay (or advance) in the arrival time of
the reference 1PPS at the CSAC (see
). Cable length
"Cable Length Compensation" (see page 13)
compensation is represented as a signed integer in units of 100 ps, with a maximum value of ±1000
(100 ns).
The sign of the compensation is such that a positive value reflects known DELAY in the arrival time of
the 1PPS. For instance, 33 feet of RG-58 cable requires compensation of +45 ns.
The format for setting the cable length compensation value is
!DCX[CRLF]
where X is the new compensation value.
Example (set cable length compensation to +15 nanoseconds):
Command:
!DC150[CRLF]
