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Altera Corporation
25
EPXA1 Development Board Hardware Reference Manual
The only device for which you cannot change the clock input is
the Ethernet. The Ethernet clock input is the 25-MHz oscillator,
X1.
Apart from selecting the clock inputs, you can also select the target
devices for each clock input.
If you plug in an alternative crystal oscillator, it drives the same
clock line as the SMA connector. To drive a clock through the
SMA connector, you must remove the alternative crystal
oscillator.
lists all the clock signals on the development board.
Table 16. EPXA1 Development Board Clocks (Part 1 of 2)
Clock Source
EPXA1 Pin
(or Board
Connection)
Signal Name
Description
Target
Device
CLK_REF
H7
CLK_REF
Main clock used to drive the embedded stripe of
the EPXA1. Dedicated input selected from
either the SMA connector or the 25 MHz crystal
oscillator using jumper CLKA Select (J13)
EPXA1
CLKA_1
U1
CLK1p
Dedicated pin that drives PLL1
EPXA1
CLKA_2
R21
CLK2p
Dedicated pin that drives PLL2
EPXA1
CLKA_3
(OSC_BUFF1)
(J3.9)
H5V_OSC
Clock to long expansion header
Long
expansion
header
CLKA_4
(OSC_BUFF2)
(J11.9)
H5V_OSC
Clock to standard expansion header
Standard
expansion
header
CLKB_0
V1
CLK3p
Dedicated pin that drives PLL3
EPXA1
CLKB_1
P21
CLK4p
Dedicated pin that drives PLL4
EPXA1
OSC_25MHZ
(U9:1)
XTAL1
Clock to Ethernet; optionally used for other
development board modules
Ethernet
CLKLK_ENA
R6
CLKLK_ENA
Clock-enable for PLL circuitry; permanently on
EPXA1
CLKLK_OUT2p U22
CLKLK_OUT2p
Dedicated pin allowing PLL2 output to be driven
off-chip, providing the PLL clock to the
expansion headers as
H5V_CLK
Standard
expansion
header,
Long
expansion
header
Summary of Contents for Excalibur EPXA1
Page 6: ...Notes ...