CLOCKADJUST

Enables clock adjustments

Platform:

OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, SPAN CPT7

Firmware Stream:   

All oscillators have some inherent drift. By default, the receiver attempts to steer the receiver’s clock to accurately match GPS reference time. Use the CLOCKADJUST command to disable this function. The TIME log can then be used to monitor clock drift.

The CLOCKADJUST command should only be used by advanced users.

  1. If the CLOCKADJUST command is ENABLED and the receiver is configured to use an external reference frequency (set in the EXTERNALCLOCK command for an external clock - TCXO, OCXO, RUBIDIUM, CESIUM, or USER), then the clock steering process takes over the VARF output pins and may conflict with a previously entered EVENTOUTCONTROL command.

  2. When using the EXTERNALCLOCK and CLOCKADJUST commands together, issue the EXTERNALCLOCK command first to avoid losing satellites.

  3. When disabled, the range measurement bias errors continue to accumulate with clock drift.

  4. Pseudorange, carrier phase and Doppler measurements may jump if the CLOCKADJUST mode is altered while the receiver is tracking.

  5. When disabled, the time reported on all logs may be offset from GPS reference time. The 1PPS output may also be offset. The amount of this offset may be determined from the TIME log.

  6. A discussion on GPS reference time may be found in GPS Reference Time Status.

Message ID: 15

Abbreviated ASCII Syntax:

CLOCKADJUST switch

Factory Default:

CLOCKADJUST ENABLE

ASCII Example:

CLOCKADJUST DISABLE

The CLOCKADJUST command can be used to calibrate an internal oscillator. Disable the CLOCKADJUST mode in order to find out what the actual drift is from the internal oscillator. Watch the CLOCKMODEL log to see the drift rate and adjust the oscillator until the drift stops.

Field

Field Type

ASCII Value

Binary Value

Description

Format

Binary Bytes

Binary Offset

1

CLOCKADJUST header

-

-

Command header. See Messages for more information.

-

H

0

2

switch

DISABLE

0

Disallow adjustment of internal clock

Enum

4

H

ENABLE

1

Allow adjustment of internal clock