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A Trimble Standard Interface Protocol
72 Trimble ThunderBolt E GPS Disciplined Clock User Guide
Command Packet 0x8E-A8 Type 0 Data Format
Command Packet 0x8E-A8 Type 1 Data Format
2 Type A "2" in this field indicates that the packet contains Recovery
Mode parameters. These parameters allow the user to control
the recovery process. During Recovery, The receiver will remove
any PPS offset accumulated during periods of Holdover by either
shifting the PPS into alignment or by shifting the frequency of
the 10 MHz oscillator by a specified amount until the PPS has
slewed back into alignment or by using both methods. The
following two parameters control these methods:
• If a fast recovery is desired, allow jam syncs to be used
• If it is important to maintain 10 million clock cycles per PPS
pulse, then disable jam syncs and set the maximum frequency
offset to a tolerable value.
Jam Sync
Threshold
This field carries the jam sync threshold in nanoseconds used
during Recovery mode. While in Recovery Mode, if the PPS offset
is above this threshold, The receiver will automatically perform a
jam sync to shift the PPS into alignment with GPS. The minimum
allowed value is 50 nanoseconds. Setting a value less than or
equal to 0 nanoseconds will disable automatic jam syncs during
Recovery (though the user can still issue a jam sync command
with packet 0x8E-A3).
Maximum
Frequency
Offset
This field carries the maximum allowable frequency offset in ppb
(parts per billion, or 1x10-9) of the 10 MHz oscillator during
Recovery Mode. While in Recovery Mode, The receiver will
remove any PPS offset accumulated during periods of Holdover
by shifting the frequency of the oscillator by an amount up to
the value specified. The minimum allowed value is 5ppb.
3 Type A "3" in this field indicates that the packet contains the initial
DAC voltage parameter.
Initial DAC
voltage
At reset, the oscillator's frequency control voltage is set to this
value
Byte Item Type Description
0Subcode UINT80xA8
1 Type UINT8 0 = loop dynamics
2-5 Time Constant Single Seconds
6-9 Damping Factor Single Dimensionless
Byte Item Type Description
0 Subcode UINT8 0xA8
1 Type UINT8 1 = oscillator parameters
2-5 Oscillator Gain Constant Single Hz/Volt
6-9 Minimum Control Voltage Single Volts
10-13 Maximum Control Voltage Single Volts
Type Data field Description