CLOCKCALIBRATE
Adjusts clock steering parameters
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Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2 |
This command is used to adjust the control parameters of the clock steering loop. The receiver must be enabled for clock steering before these values can take effect. Refer to the CLOCKADJUST command to enable or disable clock steering.
To disable the clock steering process, issue the CLOCKADJUST DISABLE command.
The current values used by the clock steering process are listed in the CLOCKSTEERING command.
The values entered using the CLOCKCALIBRATE command are saved to non-volatile memory (NVM). To restore the values to their defaults, the FRESET CLKCALIBRATION command must be used. Issuing FRESET without the CLKCALIBRATION parameter will not clear the values (see FRESET command for more details).
Message ID: 430
Abbreviated ASCII Syntax:
CLOCKCALIBRATE [mode] [period] [pulsewidth] [slope] [bandwidth]
ASCII Example:
CLOCKCALIBRATE AUTO
The receiver by default steers its INTERNAL VCTCXO but can be commanded to control an EXTERNAL reference oscillator. Use the EXTERNALCLOCK command to configure the receiver to use an external reference oscillator. If the receiver is configured for an external reference oscillator and configured to adjust its clock, then the clock steering loop attempts to steer the external reference oscillator through the use of the VARF signal. Note that the clock steering control process conflicts with the manual EVENTOUTCONTROL command and FREQUENCYOUT command. It is expected that the VARF signal is used to provide a stable reference voltage by the use of a filtered charge pump type circuit (not supplied).
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Field |
Field Type |
ASCII Value |
Binary Value |
Description |
Format |
Binary Bytes |
Binary Offset |
|
1 |
Command header |
- |
- |
CLOCKCALIBRATE header This field contains the command name for abbreviated ASCII or the message header for ASCII (see page 1) or Binary (see page 1). |
- |
H |
0 |
|
2 |
mode |
SET |
0 |
Sets the period, pulsewidth, slope and bandwidth values into NVM for the currently selected steered oscillator. (INTERNAL or EXTERNAL) |
Enum |
4 |
H |
|
AUTO |
1 |
Forces the receiver to do a clock steering calibration to measure the slope (change in clock drift rate with a 1 bit change in pulse width) and required pulsewidth to zero the clock drift rate. After the calibration, these values along with the period and bandwidth are entered into NVM and are then used from this point forward on the selected oscillator. |
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OFF |
2 |
Terminates a calibration process currently underway. (default) |
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|
3 |
period |
0 to 262144 |
Signal period in 10 ns steps. Frequency Output = 100,000,000 / Period |
Ulong |
4 |
H+4 |
|
|
4 |
pulsewidth |
The valid range for this parameter is 10% to 90% of the period |
Sets the initial pulse width that should provide a near zero drift rate from the selected oscillator being steered. The valid range for this parameter is 10% to 90% of the period. If this value is not known, (in the case of a new external oscillator) then it should be set to ½ the period and the mode should be set to AUTO to force a calibration. |
Ulong |
4 |
H+8 |
|
|
5 |
slope |
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This value should correspond to how much the clock drift changes with a 1 bit change in the pulsewidth m/s/bit. The default values for the slope used for the INTERNAL and EXTERNAL clocks is -2.0 and -0.01 respectively. If this value is not known, then its value should be set to 1.0 and the mode should be set to AUTO to force a calibration. Once the calibration process is complete and using a slope value of 1.0, the receiver should be recalibrated using the measured slope and pulsewidth values (see the CLOCKSTEERING log). This process should be repeated until the measured slope value remains constant (less than a 5% change). |
Float |
4 |
H+12 |
|
|
6 |
bandwidth |
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This is the value used to control the smoothness of the clock steering process. Smaller values result in slower and smoother changes to the receiver clock. Larger values result in faster responses to changes in oscillator frequency and faster start up clock pull in. The default values are 0.03 and 0.001 Hz respectively for the INTERNAL and EXTERNAL clocks. |
Float |
4 |
H+16 |
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