Si5345-44-42-D-RM
Rev. 1.0
29
Table 15 lists the OOF monitoring and control registers. Because the precision OOF monitor needs to provide
1/16 ppm of frequency 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.
5.3.3. Loss of Lock Fault Monitoring
The Loss of Lock (LOL) monitor asserts a LOL register bit when the DSPLL has lost synchronization with its
selected input clock. There is also a dedicated loss of lock pin that reflects the loss of lock condition. The LOL
monitor functions by measuring the frequency difference between the input and feedback clocks at the phase
detector. There are four parameters to the LOL monitor,
1. Assert to set the LOL,
a. User sets the threshold in ppm in CBPro
2. Fast assert to set the LOL
a. CBPro sets this to ~100 times the assert threshold
b. A very large ppm error in a short time will assert the LOL
3. De-assert to clear the LOL
a. User sets the threshold in ppm in CBPro
Table 15. Out-of-Frequency Status Monitoring and Control Registers
Register Name
Hex Address
[Bit Field]
Function
OOF
0x000D[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_FLG
0x0012[7:4]
OOF status monitor sticky bits for IN3, IN2, IN1, IN0. Stick bits will
remain asserted when an OOF event occurs until cleared. Writing zero
to the bit will clear it.
OOF_INTR_MSK
0x0018[7:4]
Masks OOF from generating INTR interrupt for IN3 – IN0.
0: Allow OOF interrupt (default)
1: Mask (ignore) OOF for interrupt
OOF_REF_SEL
0x0040[2:0]
This selects the clock that the OOF monitors use as the 0 ppm refer-
ence. Selections are XA/XB, IN0, IN1, IN2, IN3. Default is XAXB.
OOF_EN
0x003F[3:0]
This allows to enable/disable the precision OOF monitor for IN3, IN2,
IN1, IN0
FAST_OOF_EN
0x003F[7:4]
This allows to enable/disable the fast OOF monitor for IN3, IN2, IN1,
IN0
OOF_SET_THR
0x0046[7:0]-
0x0049[7:0]
OOF Set threshold. Range is up to
500 ppm in steps of 1/16 ppm
OOF_CLR_THR
0x004A[7:0]-
0x004D[7:0]
OOF Clear threshold. Range is up to
500 ppm in steps of 1/16 ppm
FAST_OOF_SET_THR
0x0051[7:0]-
0x0054[7:0]
Determines the fast OOF alarm set threshold for IN3, IN2, IN1, IN0.
FAST_OOF_CLR_THR
0x0055[7:0]-
0x0058[7:0]
Determines the fast OOF alarm clear threshold for IN3, IN2, IN1, IN0.