OOF
Reference
Hysteresis
Hysteresis
OOF Declared
OOF Cleared
-6 ppm
(Set)
-4 ppm
(Clear)
0 ppm
+4 ppm
(Clear)
+6 ppm
(Set)
f
IN
Figure 5.10. Example of Precise OOF Monitor Assertion and De-assertion Triggers
The table below lists the OOF monitoring and control registers. Because the precision OOF monitor needs to provide 1/16 ppm of fre-
quency measurement accuracy, it must measure the monitored input clock frequencies over a relatively long period of time. This may
be too slow to detect an input clock that is quickly ramping in frequency. An additional level of OOF monitoring called the Fast OOF
monitor runs in parallel with the precision OOF monitors to quickly detect a ramping input frequency. The Fast OOF responds more
quickly and has larger thresholds.
Table 5.9. Out-of-Frequency Status Monitoring and Control Registers
Setting Name
Hex Address [Bit Field]
Function
Si5397
Si5396
OOF Status Indicators
OOF(3,2,1,0)
000D[7:4]
000D[7:4]
OOF status monitor for IN3, IN2, IN1, IN0. Indicates if a
valid clock is detected or if a OOF condition is detected.
OOF(3,2,1,0)_FLG
0012[7:4]
0012[7:4]
OOF status monitor sticky bits for IN3, IN2, IN1, IN0.
Sticky bits will remain asserted when an OOF event oc-
curs until cleared. Writing a zero to a sticky bit will clear
it.
OOF(3,2,1,0)_INTR_MSK
0x0018[7:4]
0x0018[7:4]
Marks OOF from generating INTRb interrupt for IN3-IN0.
0: Allow OOF interrupt (default)
1: Mask (ignore) OOF for interrupt
OOF Monitor Control and Settings
OOF_REF_SEL
0040[2:0]
0040[2:0]
This selects the clock that the OOF monitors use as
their “0 ppm” reference. Selections are: XA/XB, IN0,
IN1, IN2, IN3.
OOF(3,2,1,0)_EN
003F[3:0]
003F[3:0]
This allows to enable/disable the precision OOF monitor
for IN3, IN2, IN1, IN0.
FAST_OOF(3,2,1,0)_EN
003F[7:4]
003F[7:4]
To enable/disable the fast OOF monitor for IN3, IN2,
IN1, IN0.
OOF(3,2,1,0)_SET_THR
0046[7:0] -
0049[7:0]
0046[7:0] -
0049[7:0]
Determines the OOF alarm set threshold for IN3, IN2,
IN1, IN0. Range is from ±2 ppm to ±500 ppm in steps of
2 ppm.
OOF(3,2,1,0)_CLR_THR
004A[7:0] -
004D[7:0]
004A[7:0] -
004D[7:0]
Determines the OOF alarm clear threshold for INx.
Range is from ±2 ppm to ±500 ppm in steps of 2 ppm.
FAST_OOF(3,2,1,0)_SET_THR
0x0051[7:0] -
0x0054[7:0]
0x0051[7:0] -
0x0054[7:0]
Determines the fast OOF alarm set threshold for IN3,
IN2, IN1, IN0.
FAST_OOF(3,2,1,0)_
CLR_THR
0x0055 [7:0] -
0x0058[7:0]
0x0055 [7:0] -
0x0058[7:0]
Determines the fast OOF alarm clear threshold for IN3,
IN2, IN1, IN0.
Si5397/96 Reference Manual
Clock Inputs
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