82P33731 datasheet(23/66 Pages) RENESAS

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August 28, 2017

82P33731 Datasheet

3.2.3.2

Input Clock Quality Monitoring

The qualities of all the input clocks are always monitored in the fol-

lowing aspects:

• LOS (loss of signal) (only for IN1 and IN2)

• Activity

• Frequency

LOS monitoring is only conducted on IN1 and IN2. Activity and fre-

quency monitoring are conducted on all the input clocks.

The qualified clocks are available for selection for all 3 DPLLs.

3.2.3.2.1 Loss of Signal (LOS) Monitoring

IN1 and IN2 support the AMI input signal. LOS monitoring is con-

ducted on IN1 and IN2. A LOS event occurs when the amplitude of the

input clock falls below +0.6 Vp-p for 1 ms; the LOS event is cleared

when the amplitude rises higher than +1 Vp-p.

LOS status is indicated by the AMI1_LOS / AMI2_LOS bit. If the

AMI1_LOS / AMI2_LOS bit is ‘1’, the occurrence of LOS will trigger an

interrupt.

The input clock in LOS status is disqualified for clock selection for the

DPLL.

3.2.3.2.2 Activity Monitoring

Activity is monitored by using an internal leaky bucket accumulator,

as shown in Figure 9.

Each input clock is assigned an internal leaky bucket accumulator.

The input clock is monitored for each period of 128 ms, the internal leaky

bucket accumulator is increased by 1 when an event is detected; and it

is decreased by 1 when no event is detected within the period set by the

decay rate. The event is that an input clock drifts outside (>) ±500 ppm

with respect to the system clock within a 128 ms period.

There are four configurations (0 - 3) for a leaky bucket accumulator.

The leaky bucket configuration for an input clock is selected by the cor-

responding BUCKET_SEL[1:0] bits. Each leaky bucket configuration

consists of four elements: upper threshold, lower threshold, bucket size

and decay rate.

The bucket size is the capability of the accumulator. If the number of

the accumulated events reach the bucket size, the accumulator will stop

increasing even if further events are detected. The upper threshold is a

point above which a no-activity alarm is raised. The lower threshold is a

point below which the no-activity alarm is cleared. The decay rate is a

certain period during which the accumulator decreases by 1 if no event

is detected.

The leaky bucket configuration is programmed by one of four groups

of register bits: the BUCKET_SIZE_n_DATA[7:0] bits, the UPPER_

THRESHOLD_n_DATA[7:0] bits,

the LOWER_THRESHOLD_n_

DATA[7:0] bits and the DECAY_RATE_n_DATA[1:0] bits respectively; ‘n’

is 0 ~ 3.

The no-activity alarm status of the input clock is indicated by the

INn_NO_ACTIVITY_ALARM bit (14

 n  1).

The input clock with a no-activity alarm is disqualified for clock selec-

tion for the DPLLs.

Figure 9. Input Clock Activity Monitoring

Input Clock

Leaky Bucket Accumulator

No-activity Alarm Indication

Decay

Rate

Bucket Size

Upper Threshold

Lower Threshold

clock signal with no event

clock signal with events

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