Chapter 2: Board Components
2–23
Clocking Circuitry
© March 2009 Altera Corporation
Cyclone III 3C120 Development Board Reference Manual
Clocking Circuitry
This section describes Cyclone III FPGA clocking inputs and outputs. A diagram is
provided for each section.
Cyclone III FPGA Clock Inputs
Figure 2–5
outlines the clocking inputs to the Cyclone III FPGA.
1
Some signals are connected to 1.8-V banks and some are connected to 2.5-V banks.
Refer to the
Cyclone III Device Handbook
for information about allowable levels for
driving these inputs from external sources.
The clock 1 and clock 2 signals from the HSMC interface can be used as LVDS pairs or
as eight separate clock signals. These signals include
HSMA_CLK_IN_P2/N2
,
HSMA_CLK_IN_P1/N1
,
HSMB_CLK_IN_P2/N2
, and
HSMB_CLK_IN_P1/N1
. These
signals may also be used for bidirectional data. If used in LVDS mode, install
applicable termination resistors between P/N pairs. A voltage translator, National
Semiconductor part number FXLP34, is located in between the HSMC interfaces and
the Cyclone III FPGA to reduce LVTTL to 1.8-V CMOS input levels for clock 0 signals
HSMA_CLK_IN0
and
HSMB_CLK_IN0
.
f
For more information, refer to the Cyclone III development board schematics
included in the development kit.
Figure 2–5.
Cyclone III FPGA Clock Inputs
Bank
8
1.
8
V
Bank 7
1.
8
V
Bank 3
1.
8
V
Bank 4
1.
8
V
Bank 6
2.5
V
Bank 5
2.5
V
Bank 1
2.5
V
Bank 2
2.5
V
HSMC
Port A
ENET
PHY
HSMA_CLK_IN_P2
HSMA_CLK_IN_N2
HSMA_CLK_IN_P1
HSMA_CLK_IN_N1
HSMA_CONN_CLK_IN0
HSMA_CLK_IN0
HSMC
Port B
HSMB_CLK_IN_P1
HSMB_CLK_IN_N1
HSMA_CLK_IN_P2
HSMA_CLK_IN_N2
ENET_RX_CLK
CLKIN_SMA
CLKIN_50
MAX II CPLD
BUF
SMA Inp
u
t 50
MHz
CLKIN_125
USB_IFCLK
125 MHz
3.3
V
1.
8V
HSMB_CLK_IN0
HSMB_CONN_CLK_IN0
BUF
3.3
V
1.
8
V
CLK0
CLK1
CLK2
CLK3
CLK4
CLK
8
CLK9
CLK10
CLK11
CLK12
CLK13
CLK14
CLK5
CLK6
CLK7
CLK15
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