ACS8530 datasheet(91/152 Pages) SEMTECH

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ADVANCED COMMUNICATIONS

FINAL

DATASHEET

Revision 3.02/November 2005 © Semtech Corp.

Page 91

www.semtech.com

ACS8530 SETS

Address (hex):

Description

(R/W) Register to control the

Holdover modes of the T0 DPLL.

Default Value

1000 1000

Bit 7Bit 6

Bit 5Bit 4

Bit 3

Bit 2Bit 1Bit 0

auto_averaging fast_averaging

read_average

mini_holdover_mode

holdover_frequency_value [18:16]

Bit No.

Description

Bit Value

Value Description

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).

Averaged frequency not used, Holdover frequency

either manual or instantaneously frozen.

Averaged frequency used, providing manual

Holdover mode is not engaged.

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.

Slow Holdover frequency averaging enabled.

Fast Holdover frequency averaging enabled.

read_average

Bit to control whether the value read from the

holdover_frequency_value register is the value

written to that register, or the averaged Holdover

frequency. This allows software to use the internal

averager as part of the Holdover algorithm, but use

manual Holdover mode plus software to enhance

the performance.

Value read from a holdover_frequency_value is the

value written to it.

Value read from a holdover_frequency_value is

either the fast or slow averaged frequency as

determined by fast_averaging.

[4:3]

mini_holdover_mode

Mini-holdover is a term used to describe the state of

the DPLL when it is in locked mode, but it has

temporarily lost its input. This may be a temporary

state, or last for many seconds whilst an input is

checked for inactivity. The DPLL behaves exactly as

in Holdover, and the frequency can be determined

in the same selection of ways (instantaneously, fast

averaged or slow averaged).

Mini-holdover frequency determined in the same

way as for full Holdover mode.

Mini-holdover frequency frozen instantaneously.

Mini-holdover frequency taken from fast averager.

Mini-holdover frequency taken from slow averager.

[2:0]

holdover_frequency_value [18:16]

See Reg. 3F (cnfg_holdover_frequency) for details.

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