4. Clock Network
The Intel Stratix 10 E-Tile transceivers are equipped with the following clock networks:
•
Reference clock
•
Core interface clock
4.1. Reference Clock Pins
There are nine LVPECL reference clock pins on every Intel Stratix 10 E-Tile. You can
configure the pins as either 2.5-V LVPECL compliant or 3.3-V LVPECL tolerant. There
are source terminations (RS1 and RS2, 50 Ω each) and load terminations (RL1 and
RL2, 250 Ω each), as well as built-in internal AC coupling for differential reference
clock input pairs. Intel recommends using the default setting, which is internal source
termination at 2.5 V. Carefully disable internal source termination only when you need
external termination at 3.3 V (or 2.5 V). For external termination and related
reference clock detailed requirements, refer to the Intel Stratix 10 GX, MX, TX, and SX
Device Family Pin Connection Guidelines.
The Intel Stratix 10 E-Tile transceiver reference clock input pin supports a frequency
range of 125 MHz to 700 MHz, but the reference clock network supports a maximum
frequency of 500 MHz. Whenever you configure a reference clock frequency of greater
than 500 MHz, the Divide by 2 block is automatically instantiated in the back end.
The hardware supports nine reference clocks pins, but the Native PHY IP core
parameter editor provides any five reference clocks for a given design implementation.
You select which five based on your board layout.
Figure 49.
IO Pad Ring - Transceiver Reference Clock Input Pad
Reference Clock Buffer
+
–
REFCLK
PAD
REFCLK_N
PAD_N
Reference
Clock
Network
RS1
RS2
RL1
RL2
Divide
by 2
C1
C2
E-Tile completes the power-up configuration successfully as long as a valid reference
clock frequency, 125 MHz - 500 MHz (if the
refclk
Divide by 2 is disabled) or 250
MHz - 700 MHz (if the
refclk
Divide by 2 is enabled), is available during device
UG-20056 | 2019.02.04
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