SI5364 Datasheet, PDF (29/40 Pages) Silicon Laboratories – SONET/SDH PRECISION PORT CARD CLOCK IC

Si5364
Pin #
Pin Name
Table 10. Pin Descriptions (Continued)
I/O
Signal Level
Description
B1
AUTOSEL
I*
LVTTL
Automatic Switching Mode Select.
When 1, the clock input used by the DSPLL to gener-
ate the SONET/SDH clock outputs is selected auto-
matically. The automatic switching mode initially
selects the highest priority clock available, with the
priorities indicated below:
CLKIN_A: Highest Priority
CLKIN_B: Second Highest Priority
REF/CLKIN_F: Lowest Priority
If the selected input clock fails because of an LOS or
FOS alarm condition, the next lower priority clock
that is available is selected.
If an input clock that has a higher priority than the
currently-selected clock becomes available, the
higher priority clock is selected only if RVRT is
active. If RVRT is not active, automatic switching to a
higher priority clock is disabled.
A7
A_ACTV
O
LVTTL
CLKIN_A is Active.
Active high output indicates that CLKIN_A is
selected as the clock input to the DSPLL.
The DH_ACTV output takes precedence over this
signal as an indicator of the DSPLL clock input sta-
tus. When this output is high and the DH_ACTV out-
put is low, CLKIN_A is being used by the DSPLL to
generate the SONET/SDH compatible output clocks.
When this output is high and the DH_ACTV output is
high, CLKIN_A is selected, but the DSPLL is in digi-
tal hold mode. See DH_ACTV.
A8
B_ACTV
O
LVTTL
CLKIN_B is Active.
Active high output indicates that CLKIN_B is
selected as the clock input to the DSPLL.
The DH_ACTV output takes precedence over this
signal as an indicator of the DSPLL clock input sta-
tus. When this output is high and the DH_ACTV out-
put is low, CLKIN_B is being used by the DSPLL to
generate the SONET/SDH compatible output clocks.
When this output is high and the DH_ACTV output is
high, CLKIN_B is selected, but the DSPLL is in
digital hold mode. See DH_ACTV.
*Note: The LVTTL inputs on the Si5364 device have an internal pulldown mechanism that causes the input to default to a logic
low state if the input is not driven from an external source.
Rev. 2.2
29