ACS8520 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'ACS8520' PDF : 150 Pages View PDF
ACS8520 SETS
ADVANCED COMMUNICATIONS
Address (hex): 3F
Register Name cnfg_holdover_frequency
[15:8]
FINAL
DATASHEET
Description
(R/W) Bits [15:8] of the manual Default Value 0000 0000
Holdover frequency register.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
holdover_frequency_value[15:8]
Bit 2
Bit 1
Bit 0
Bit No.
Description
Bit Value Value Description
[7:0]
holdover_frequency_value[15:8]
This value in this register is combined with the value
in Reg. 3E and Bits [2:0] of Reg. 40 to represent the
programmed Holdover frequency of the T0 DPLL.
This register is designed such that software can
read the sts_current_DPLL_frequency register
(Reg. 0C, Reg. 0D and Reg. 07) and filter the value.
The result will then be in a suitable format to simply
write back to the cnfg_holdover_frequency register.
*This register can be programmed to read back the
internally averaged Holdover frequency rather than
the programmed value, see Bit 5 of Reg. 40
cnfg_holdover_modes.
-
In order to calculate the Holdover ppm offset of the
DPLL with respect to the crystal oscillator frequency,
the value in Reg. 3E hex and Bits [2:0] of Reg. 40
need to be concatenated. This value is a 2’s
complement signed integer. The value multiplied by
0.0003068 dec will give the value in ppm.
Address (hex): 40
Register Name cnfg_holdover_modes
Description
(R/W) Register to control the
Default Value 1000 1000
Holdover modes of the T0 DPLL.
Bit 7
Bit 6
Bit 5
auto_averaging fast_averaging read_average
Bit 4
Bit 3
mini_holdover_mode
Bit 2
Bit 1
Bit 0
holdover_frequency_value [18:16]
Bit No.
Description
Bit Value Value Description
7
auto_averaging
Bit to enable the use of the averaged frequency
value during Holdover. This bit is overridden by the
manual Holdover control (Bit 4, man_holdover, in
Reg. 34).
6
fast_averaging
Bit to control the rate of averaging of the Holdover
frequency. Fast averaging gives a -3db response
point of approximately 8 minutes. Slow averaging
give a -3db response point of approximately 110
minutes.
0
Averaged frequency not used, Holdover frequency
either manual or instantaneously frozen.
1
Averaged frequency used, providing manual
Holdover mode is not engaged.
0
Slow Holdover frequency averaging enabled.
1
Fast Holdover frequency averaging enabled.
Revision 3.02/October 2005 © Semtech Corp.
Page 90
www.semtech.com
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