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Altera Phase-Locked Loop (Altera PLL) IP Core User
Guide
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The Altera PLL megafunction IP core allows you to configure the settings of PLL.
Altera PLL IP core supports the following features:
• Supports six different clock feedback modes: direct, external feedback, normal, source synchronous,
zero delay buffer, and LVDS mode.
• Generates up to 18 clock output signals for the Arria® V and Stratix® V devices and nine clock output
signals for the Cyclone® V device.
• Switches between two reference input clocks.
• Supports both the adjacent PLL (adjpllin) and the C-Counter clock source (cclk) inputs to connect
with an upstream PLL in PLL cascading mode.
• Supports PLL output cascading.
• Generates the Memory Initialization File (.mif) and allows PLL dynamic reconfiguration.
Related Information
• Introduction to Altera IP Cores
Provides more information about the Altera IP cores and the parameter editor.
• Operation Modes on page 9
• Output Clocks on page 9
• Reference Clock Switchover on page 10
• PLL-to-PLL Cascading on page 10
• PLL Output Counter Cascading on page 14
Device Family Support
The Altera PLL IP core supports the Arria V, Cyclone V, and Stratix V device families.
Altera PLL IP Core Parameters
The Altera PLL IP core parameter editor appears in the PLL category of the IP Catalog.
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Altera PLL IP Core Parameters - General Tab
Altera PLL IP Core Parameters - General Tab
Table 1: Altera PLL IP Core Parameters - General Tab
Parameter Legal Value Description
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Device Speed Grade Stratix V: 1–4,
Arria V: 3–6,
Specifies the speed grade for a device. The lower the
number, the faster the speed grade.
Cyclone V: 6–
8
PLL Mode Integer-N PLL
or Fractional-
Specifies the mode used for the Altera PLL IP core. The
default mode is Integer-N PLL.
N PLL
Reference Clock Frequency — Specifies the input frequency for the input clock, refclk, in
MHz. The default value is 100.0 MHz. The minimum and
maximum value is dependent on the selected device. The
PLL reads only the numerals in the first six decimal places.
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Altera PLL IP Core Parameters - General Tab
Parameter Legal Value Description
3
Operation Mode direct,
external
feedback,
normal,
source
synchronous,
zero delay
buffer, or lvds
Specifies the operation of the PLL. The default operation is
direct mode.
• If you select the direct mode, the PLL minimizes the
length of the feedback path to produce the smallest
possible jitter at the PLL output.The internal-clock and
external-clock outputs of the PLL are phase-shifted with
respect to the PLL clock input. In this mode, the PLL
does not compensate for any clock networks.
• If you select the normal mode, the PLL compensates for
the delay of the internal clock network used by the clock
output. If the PLL is also used to drive an external clock
output pin, a corresponding phase shift of the signal on
the output pin occurs.
• If you select the source synchronous mode, the clock
delay from pin to I/O input register matches the data
delay from pin to I/O input register.
• If you select the external feedback mode, you must
connect the fbclk input port to an input pin. A boardlevel connection must connect both the input pin and
external clock output port, fboutclk. The fbclk port is
aligned with the input clock.
• If you select the zero delay buffer mode, the PLL must
feed an external clock output pin and compensate for the
delay introduced by that pin. The signal observed on the
pin is synchronized to the input clock. The PLL clock
output connects to the altbidir port and drives
zdbfbclk as an output port. If the PLL also drives the
internal clock network, a corresponding phase shift of
that network occurs.
• If you select the lvds mode, the same data and clock
timing relationship of the pins at the internal SERDES
capture register is maintained. The mode compensates
for the delays in LVDS clock network, and between the
data pin and clock input pin to the SERDES capture
register paths.
Enable locked output port
Turn on or
Turn off
Enable physical output
clock parameters
Turn on or
Turn off
Number of Clocks Stratix V and
Arria V: 1–18,
Cyclone V: 1–
9
Altera Phase-Locked Loop (Altera PLL) IP Core User Guide
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Turn on to enable the locked port.
Turn on to enter physical PLL counter parameters instead of
specifying a desired output clock frequency.
Specifies the number of output clocks required for each
device in the PLL design. The requested settings for output
frequency, phase shift, and duty cycle are shown based on
the number of clocks selected.
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Altera PLL IP Core Parameters - Clock Switchover Tab
Parameter Legal Value Description
Desired Frequency
(1)
— Specifies the output clock frequency of the corresponding
output clock port, outclk[], in MHz. The default value is
100.0 MHz. The minimum and maximum values depend on
the device used. The PLL only reads the numerals in the first
six decimal places.
Actual Frequency — Specifies the actual value for the output clock frequency.
Phase Shift units ps or degrees Specifies the phase shift unit for the corresponding output
clock port, outclk[], in picoseconds (ps) or degrees.
Phase Shift — Specifies the requested value for the phase shift. The default
value is 0 ps.
Actual Phase Shift — Specifies the actual value for the phase shift.
Duty Cycle 1–99 Specifies the duty cycle in percentage for the corresponding
output clock port, outclk[]. The default value is 50%.
Fractional carry out
(2)(3)
8, 16, 24, or 32 Specifies the fractional carry out (Fcout) for the Delta Sigma
Modulator (DSM) mode for PLL. The fractional carry out
determines the denominator in the equation K/2^Fcout.
DSM Order
(2)(3)
1st_order,
2nd_order,
Specifies the DSM order for shifting the fractional noise to
be filtered out by the PLL to high frequencies.
3rd_order, or
disable
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Multiply Factor (MCounter)
(3)
Fractional Multiply Factor
(2)(3)
(K)
Divide Factor (N-
Counter)
(3)
Make this a cascade
counter
(3)(4)
Divide Factor (CCounter)
(3)
1-512 Specifies the multiply factor of M-counter.
1 to (2^Fcout-1)Specifies the fractional multiply factor of DSM. Fcout is the
value of fractional carry out parameter.
1-512 Specifies the divide factor of N-counter.
Turn on or
Turn off
Turn on to cascade this counter into the next counter
output for larger division factor.
1-512 Specifies the divide factor for the output clock (C-counter)
Altera PLL IP Core Parameters - Clock Switchover Tab
Table 2: Altera PLL IP Core Parameters - Clock Switchover Tab
Parameter Legal Value Description
Create a second input clk
‘refclk1’
(1)
This parameter is only available when Enable physical output clock parameters is turned off.
(2)
This parameter is only available in Fractional-N PLL mode.
(3)
This parameter is only available when Enable physical output clock parameters is turned on.
(4)
This feature is only supported in Quartus® II version 13.1 and onwards.
Turn on or
Turn off
Turn on to provide a backup clock attached to your PLL
that can switch with your original reference clock.
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Altera PLL IP Core Parameters - Clock Switchover Tab
Parameter Legal Value Description
5
Second Reference Clock
Frequency
Switchover Mode
—
Automatic
Switchover,
Manual
Switchover, or
Automatic
Switchover
with Manual
Override
Selects the frequency of the second input clock signal. The
default value is 100.0 MHz. The minimum and maximum
value is dependent on the device used. The PLL reads only
the numerals in the first six decimal places.
The PLL is automatically configured to satisfy its legality
requirements for the primary reference clock only. If the
second reference clock frequency is different, this may cause
an illegal VCO or PFD frequency error. To avoid this error,
you can turn on Enable physical output clock parameters
and manually configure the PLL such that the frequency is
legal for both refclk inputs.
Specifies the switchover mode for design application. The IP
supports three switchover modes:
• If you select the Automatic Switchover mode, the PLL
circuitry monitors the selected reference clock. If one
clock stops, the circuit automatically switches to the
backup clock in a few clock cycles and updates the status
signals, clkbad and activeclk.
• If you select the Manual Switchover mode, when the
control signal, extswitch, changes from logic low to
logic high, and stays high for at least three clock cycles,
the input clock switches to the other clock. The
extswitch can be generated from FPGA core logic or
input pin.
• If you select Automatic Switchover with Manual
Override mode, when the extswitch signal is high, it
overrides the automatic switch function. As long as
extswitch remains high, further switchover action is
blocked. To select this mode, your two clock sources
must be running and the frequency of the two clocks
cannot differ by more than 20%. If both clocks are not on
the same frequency, but their period difference is within
20%, the clock loss detection block will detect the lost
clock. The PLL most likely drops out of lock after the
PLL clock input switchover and needs time to lock again.
Switchover Delay
Create an ‘active_clk’ signal
to indicate the input clock
0–7 Adds a specific amount of cycle delay to the switchover
Turn on or
Turn off
in use
Create a ‘clkbad’ signal for
each of the input clocks
Altera Phase-Locked Loop (Altera PLL) IP Core User Guide
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Turn on or
Turn off
process. The default value is 0.
Turn on to create the activeclk output. The activeclk
output indicates the input clock which is in use by the PLL.
Output signal low indicates refclk and output signal high
indicates refclk1.
Turn on to creates two clkbad outputs, one for each input
clock. Output signal low indicates the clock is working and
output signal high indicates the clock is not working.
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Altera PLL IP Core Parameters - Cascading Tab
Altera PLL IP Core Parameters - Cascading Tab
Table 3: Altera PLL IP Core Parameters - Cascading Tab
Parameter Legal Value Description
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Create a ‘cascade out’ signal
to connect with a
downstream PLL
Specifies which outclk to be
used as cascading source
Turn on or
Turn off
Stratix V and
Arria V: 1–18,
Turn on to create an output port, which indicates that this
PLL will be used as a source and it connects with a destina‐
tion (downstream) PLL.
Specifies the cascading source.
Cyclone V: 1–
9
Create an adjpllin or cclk
signal to connect with an
upstream PLL
PLL Cascading Mode Create an
Turn on or
Turn off
adjpllin signal
to connect
with an
upstream PLL
or Create a
cclk signal to
Turn on to create an input port, which indicates that this
PLL will be used as a destination and it connects with a
source (upstream) PLL.
• If you select Create an adjpllin signal to connect with
an upstream PLL, the adjpllin signal is created to
connect with an upstream PLL during cascading.
• If you select Create a cclk signal to connect with an
upstream PLL, the cclk
with an upstream PLL during cascading.
connect with
an upstream
PLL
Altera PLL IP Core Parameters - MIF Streaming Tab
(5)
signal is created to connect
Table 4: Altera PLL IP Core Parameters - MIF Streaming Tab
Parameter Legal Value Description
Generate MIF file Turn on or
Turn off
Turn on to generate the .mif for the current PLL profile. You
must turn on the Enable dynamic reconfiguration of PLL
parameter in the Settings tab before selecting this function.
The generated .mif contains a PLL profile, and a collection of
physical parameters—such as M, N, C, K, bandwidth, and
charge pump—that defines that PLL. You can then load
this .mif into the Altera PLL Reconfig IP core.
Enable Dynamic Phase
Shift for MIF Streaming
Turn on or
Turn off
Turn on to store dynamic phase shift properties for PLL
reconfiguration. You must turn on the Enable dynamic
reconfiguration of PLL parameter in the Settings tab
before selecting this function.
DPS Counter Selection C0–C17, All
Selects the counter to undergo dynamic phase shift.
C, or M
(5)
Not supported in Cyclone V devices.
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Altera PLL IP Core Parameters - Settings Tab
Parameter Legal Value Description
7
Number of Dynamic Phase
Shifts
— Selects the number of phase shift increments. The size of a
single phase shift increment is equal to 1/8 of the VCO
period. The default value is 1.
Dynamic Phase Shift
Direction
Positive or
Negative
Determines the dynamic phase shift direction to store into
the PLL MIF.
Altera PLL IP Core Parameters - Settings Tab
Table 5: Altera PLL IP Core Parameters - Settings Tab
Parameter Legal Value Description
PLL Auto Reset On or Off Automatically self-resets the PLL on loss of lock.
PLL Bandwidth Preset Auto, High,
Low, or
Medium
Enable dynamic reconfigu‐
ration of PLL
Enable access to dynamic
phase shift ports
Enable access to PLL DPA
output port
Turn on or
Turn off
Turn on or
Turn off
Turn on or
Turn off
Specifies the PLL bandwidth preset setting. The default
setting is Auto.
Turn on to enable the dynamic reconfiguration of the PLL.
Turn on to enable the dynamic phase shift interface with the
PLL.
Turn on to enable the eight bits port for the eight phases of
the DPA clock.
PLL DPA output division 1, 2, or 4 Specifies the PLL DPA output division value.
Related Information
• AN 661: Implementing Fractional PLL Reconfiguration with Altera PLL and Altera PLL Reconfig
IP Cores
Provides more information about PLL dynamic reconfiguration and dynamic phase shift.
• Dynamic Phase Shift Signals in Altera PLL IP Core
Altera PLL IP Core Parameters - Advanced Parameters Tab
Table 6: Altera PLL IP Core Parameters - Advanced Parameters Tab
Parameter Legal Value Description
Advanced Parameters — Displays a table of physical PLL settings that will be
implemented based on your input.
Functional Description
A PLL is a frequency-control system that generates an output clock by synchronizing itself to an input
clock. The PLL compares the phase difference between the input signal and the output signal of a voltagecontrolled oscillator (VCO). The PLL performs phase synchronization to maintain a constant phase angle
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F
IN
F
FB
F
REF
Up
Down
F
VCO
Pre-scale
Counter
(N)
# of
output
clocks
Phase
Frequency
Detector
(PFD)
Charge Pump
Loop Filter
and VCO
Feedback
Counter
(M)
Post-scale
Counter
(C)
Post-scale
Counter
(C)
VCO Phase Selection
at Each PLL Output Port
8
Building Blocks of a PLL
(lock) on the frequency of the input or reference signal. The synchronization or negative feedback loop of
the system forces the PLL to be phase-locked.
You can configure PLLs as frequency multipliers, dividers, demodulators, tracking generators, or clock
recovery circuits. You can use PLLs to generate stable frequencies, recover signals from a noisy communi‐
cation channel, or distribute clock signals throughout your design.
Building Blocks of a PLL
The main blocks of the PLL are the phase frequency detector (PFD), charge pump, loop filter, VCO, and
counters, such as a feedback counter (M), a pre-scale counter (N), and post-scale counters (C). The PLL
architecture depends on the device you use in your design.
Figure 1: Typical PLL Architecture
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The following terms are commonly used to describe the behavior of a PLL:
• PLL lock time—also known as the PLL acquisition time. PLL lock time is the time for the PLL to attain
the target frequency and phase relationship after power-up, after a programmed output frequency
change, or after a PLL reset.
Note:
Simulation software does not model a realistic PLL lock time. Simulation shows an unrealisti‐
cally fast lock time. For the actual lock time specification, refer to the device datasheet.
• PLL resolution—the minimum frequency increment value of a PLL VCO. The number of bits in the M
and N counters determine the PLL resolution value.
• PLL sample rate—the F
correction in the PLL. The PLL sample rate is f
Related Information
Phase-Locked Loop Basics, PLL page of the Altera website
Provides more information about the PLL building blocks.
sampling frequency required to perform the phase and frequency
REF
/N.
REF
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PLL Lock
The PLL lock is dependent on the two input signals in the phase frequency detector. The lock signal is an
asynchronous output of the PLLs.
The number of cycles required to gate the lock signal depends on the PLL input clock which clocks the
gated-lock circuitry. Divide the maximum lock time of the PLL by the period of the PLL input clock to
calculate the number of clock cycles required to gate the lock signal.
Operation Modes
The Altera PLL IP core supports six different clock feedback modes. Each mode allows clock multiplica‐
tion and division, phase shifting, and duty-cycle programming.
The following list describes the operation modes for the Altera PLL IP core:
• Direct mode—the PLL minimizes the feedback path length to produce the smallest possible jitter at the
• Normal mode—the PLL feedback path source is a global or regional clock network, minimizing clock
• Source-Synchronous mode—the data and clock signals arrive at the input pins at the same time. In this
• External Feedback mode—the PLL compensates for the fbclk feedback input to the PLL, thus
• Zero-Delay Buffer mode—the PLL feedback path is confined to the dedicated PLL external output pin.
• LVDS mode— maintains the same data and clock timing relationship of the pins at the internal
PLL Lock
PLL output. In this mode, the PLL does not compensate for any clock networks.
delay from the input clock pin to the core registers through global or regional clock network.
mode, the signals have the same phase relationship at the clock and data ports of any Input Output
Enable register.
minimizing the delay between the input clock pin and the feedback clock pin.
The clock port driven off-chip is phase aligned with the clock input for a minimal delay between the
clock input and the external clock output.
SERDES capture register. This mode compensates for the LVDS clock network delay, plus any delay
difference between the data pin and clock input pin to the SERDES capture register paths. The
compensation mimic path mimics the clock and data delay of the receiver side.
9
Related Information
• Clock Feedback Modes, Clock Networks and PLLs in Arria V Devices chapter
• Clock Feedback Modes, Clock Networks and PLLs in Cyclone V Devices chapter
• Clock Feedback Modes, Clock Networks and PLLs in Stratix V Devices chapter
Output Clocks
The Altera PLL IP core can generate up to 18 clock output signals for the Stratix V and Arria V devices,
and nine clock output signals for the Cyclone V devices. The generated clock output signals clock the core
or the external blocks outside the core.
You can use the reset signal to reset the output clock value to 0 and disable the PLL output clocks.
Each output clock has a set of requested settings where you can specify the value of output frequency,
phase shift, and duty cycle. The requested settings are the settings that you want to implement in your
design.
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Reference Clock Switchover
The actual frequency is the closest frequency setting (best approximate of the requested settings) that can
be implemented in the PLL circuit.
The output frequencies are not exact when the PLL is in fractional mode. You must be cautious with
appliances that require frequencies to be exact to within less than 0.5 Hz.
For applications that require more precise clock output frequencies, turn on Enable physical output
clock parameters in the parameter editor.
Related Information
• Arria V PLLs, Clock Networks and PLLs in Arria V Devices chapter
• Cyclone V PLLs, Clock Networks and PLLs in Cyclone V Devices chapter
• Stratix V PLLs, Clock Networks and PLLs in Stratix V Devices chapter
Reference Clock Switchover
The reference clock switchover feature allows the PLL to switch between two reference input clocks. Use
this feature for clock redundancy, or for a dual clock domain application such as in a system. The system
can turn on a redundant clock if the primary clock stops running.
Using the reference clock switchover feature, you can specify the frequency for the second input clock,
and select the mode and delay for the switchover.
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The clock loss detection and reference clock switchover block has the following functions:
• Monitors the reference clock status. If the reference clock fails, the clock automatically switches to a
backup clock input source. The clock updates the status of the clkbad and activeclk signals to alert
the event.
• Switches the reference clock back and forth between two different frequencies. Use the extswitch
signal to manually control the switch action. After a switchover occurs, the PLL may lose lock
temporarily and then regain lock.
PLL-to-PLL Cascading
The Altera 28 nm devices instantiate the Altera PLL IP core to allow cascading for PLLs in normal or
direct mode through the Global Clock (GCLK) network.
If you cascade PLLs in your design, the source (upstream) PLL must have a low-bandwidth setting, while
the destination (downstream) PLL must have a high-bandwidth setting. During cascading, the output of
source PLL serves as the reference clock (input) of the destination PLL. The bandwidth settings of
cascaded PLLs must be different. If the bandwidth settings of the cascaded PLLs are the same, the
cascaded PLLs may amplify phase noise at certain frequencies.
The Altera PLL IP core allows you to choose the following input clock sources to cascade with an
upstream PLL:
• adjpllin—for inter-cascading between fracturable fractional PLLs.
• cclk—for intra-cascading within fracturable fractional PLLs.
The cclk input clock source is not supported in Cyclone V devices.
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Table 7: adjpllin Cascading for Supported Devices
Device adjpllin Cascading (Upstream PLL — Downstream PLL)
PLL-to-PLL Cascading
11
• Arria V GX B5 and B7
• Arria V GT D7
Arria V GZ E5 and E7
• Arria V SX B3 and B5
• Arria V ST D3 and D5
• Cyclone V E A5
• Cyclone V GX C4 and C5
• Cyclone V GT D5
• Cyclone V E A7
• Cyclone V GX C7
• Cyclone V GT D7
• Cyclone V E A9
• Cyclone V GX C9
• Cyclone V GT C9
• FRACTIONALPLL_X0_Y96 — FRACTIONALPLL_X0_Y63
• FRACTIONALPLL_X183_Y96 — FRACTIONALPLL_X183_Y63
• FRACTIONAL_X0_Y31 — FRACTIONALPLL_X0_Y46
• FRACTIONALPLL_X202_Y31 — FRACTIONALPLL_X202_Y46
FRACTIONALPLL_X0_Y96 — FRACTIONALPLL_X0_Y63
FRACTIONALPLL_X0_Y14 — FRACTIONALPLL_X0_Y30
FRACTIONALPLL_X0_Y15 — FRACTIONALPLL_X0_Y32
• FRACTIONALPLL_X0_Y22 — FRACTIONALPLL_X0_Y39
• FRACTIONALPLL_X0_Y64 — FRACTIONALPLL_X0_Y81
• Stratix V GS D5
• Stratix V GX A3 (with 36
transceivers) and A4
Stratix V GX B5 and B6
• Stratix V GT C5 and C7
• Stratix V GX A5 and A7
Stratix V GS D6 and D8 Devices
• FRACTIONALPLL_X0_Y31 — FRACTIONALPLL_X0_Y46
• FRACTIONALPLL_X202_Y31 — FRACTIONALPLL_X202_Y46
• FRACTIONALPLL_X0_Y14 — FRACTIONALPLL_X0_Y30
• FRACTIONALPLL_X0_Y76 — FRACTIONALPLL_X0_Y63
• FRACTIONALPLL_X0_Y100 — FRACTIONALPLL_X0_Y85
• FRACTIONALPLL_X197_Y14 — FRACTIONALPLL_X197_Y30
• FRACTIONALPLL_X197_Y76 — FRACTIONALPLL_X197_Y63
• FRACTIONALPLL_X197_Y100 — FRACTIONALPLL_X197_Y85
• FRACTIONALPLL_X0_Y29 — FRACTIONALPLL_X0_Y44
• FRACTIONALPLL_X0_Y91 — FRACTIONALPLL_X0_Y75
• FRACTIONALPLL_X210_Y29 — FRACTIONALPLL_X210_Y44
• FRACTIONALPLL_X210_Y91 — FRACTIONALPLL_X210_Y75
• FRACTIONALPLL_X0_Y41 — FRACTIONALPLL_X0_56
• FRACTIONALPLL_X0_Y103 — FRACTIONALPLL_X0_Y87
• FRACTIONALPLL_X208_Y41 — FRACTIONALPLL_X208_56
• FRACTIONALPLL_X208_Y103 — FRACTIONALPLL_X208_Y87
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PLL-to-PLL Cascading
Device adjpllin Cascading (Upstream PLL — Downstream PLL)
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• Stratix V E E9 and EB
• Stratix V GX A9, AB, B9, and BB
• FRACTIONALPLL_X0_Y38 — FRACTIONALPLL_X0_Y52
• FRACTIONALPLL_X0_Y99 — FRACTIONALPLL_X0_Y86
• FRACTIOANLPLL_X0_Y124 — FRACTIONALPLL_X0_Y108
(6)
• FRACTIONALPLL_X225_Y38 — FRACTIONALPLL_X225_Y52
• FRACTIONALPLL_X225_Y99 — FRACTIONALPLL_X225_Y86
• FRACTIOANLPLL_X225_Y124 — FRACTIONALPLL_X225_Y108
(6)
(6)
This PLL is not available for Stratix V E E9 and EB devices, and Stratix V GX A9 and AB devices.
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adjpllin Cascadingcclk Cascading
Output Counter 17
Upstream PLL
cclk Port
adjpllin Port
Downstream PLL
Upstream PLL
Downstream PLL
Output Counter 4
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Figure 2: PLL cclk Cascading and adjpllin Cascading Modes
PLL-to-PLL Cascading
13
The clock input to PLL comes from the clock input multiplexers. The clock input multiplexers provide
multiple clock sources as reference clock inputs for fractional PLL.
Table 8: Reference Clock Inputs for Fractional PLL
Sources Description
Altera Phase-Locked Loop (Altera PLL) IP Core User Guide
coreclkin Core reference clock from clock network.
adjpllin Adjacent fractional PLL clock source.
refclkin[0] Clock source from adjacent PMA triplet LVPECL buffer.
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PLL Output Counter Cascading
Sources Description
refclkin[1] Clock source from adjacent PMA triplet LVPECL buffer.
clkin[0] Dedicated clock input for fractional PLL from regular I/O.
clkin[1] Dedicated clock input for fractional PLL from regular I/O.
clkin[2] Dedicated clock input for fractional PLL from regular I/O.
clkin[3] Dedicated clock input for fractional PLL from regular I/O.
rxiqclk Clock source from adjacent PMA triplet rxiqclknet. For
refclk and PMA/LC cascading with fractional PLL.
refiqclk Clock source from adjacent PMA triplet rxiqclknet as
refclk.
iqtxrxclk Clock source from adjacent PMA triplet iqtxrxclk as
refclk.
(7)
cclk
C-Counter clock source.
PLL Output Counter Cascading
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The Altera 28 nm devices instantiate the Altera PLL IP core to allow output counter cascading. PLL
cascading enables PLL to synthesize a lower frequency output which is not achievable with a single
counter output.
This feature is only accessible when Enable physical output clock parameters is turned on. Turn on
Make this a cascade counter to select an outclk port as the upstream counter. The upstream counter
serves as the reference clock to the downstream counter and not available as a PLL output.
Only the upstream counter in the PLL output counter cascade chain supports phase shifting and only the
downstream counter in the cascade chain support programmable duty cycle.
(7)
Not supported in Cyclone V devices.
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Upstream Counter
Downstream Counter
PLL Output Counter
Cascade Chain
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Figure 3: PLL Output Counter Cascading Mode
PLL Output Counter Cascading
15
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16
Ports
Ports
Table 9: Altera PLL Ports
Port Name Type Condition Description
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fbclk Input Optional
fboutclk Output Optional
locked Output Optional
The external feedback input port for the PLL.
The Altera PLL IP core creates this port when
the PLL is operating in external feedback mode
or zero-delay buffer mode. To complete the
feedback loop, a board-level connection must
connect the fbclk port and the external clock
output port of the PLL.
The port that feeds the fbclk port through the
mimic circuitry.
The fboutclk port is available only if the PLL is
in external feedback mode.
The Altera PLL IP core drives this port high
when the PLL acquires lock. The port remains
high as long as the PLL is locked.
The PLL asserts the locked port when the phases
and frequencies of the reference clock and
feedback clock are the same or within the lock
circuit tolerance. When the difference between
the two clock signals exceeds the lock circuit
tolerance, the PLL loses lock.
outclk[] Output Required The clock output of the PLL. The frequency of
refclk Input Required The reference clock that drives the clock
reset Input Required The asynchronous reset port for the output
zdbfbclk Bidirectional Optional
refclk1 Input Required Second input clock signal that feeds into the PLL.
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the output clock depends on the parameter
settings.
network.
clocks. Drive this port high to reset all output
clocks to the initial value of 0.
The bidirectional port that connects to the
mimic circuitry. This port must connect to a
bidirectional pin that is placed on the positive
feedback dedicated output pin of the PLL.
The zdbfbclk port is available only if the PLL is
in zero-delay buffer mode.
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Port Name Type Condition Description
extswitch Input Required Assert this input signal high (1’b1) to manually
activeclk Output Optional Output signal to determine which input clock is
clkbad Output Optional Output signal to determine which input clock is
(8)
cclk
adjpllin Input Optional Adjacent fractional PLL clock source.
cascade_out Output Optional Output signal to feed into other fractional PLLs.
Document Revision History
Document Revision History
switch the clock for at least 3 cycles.
in use by the PLL.
working.
Input Optional C-Counter clock source from the fracturable
fractional PLL output counter 4 or 13.
This port acts as a bus port when the upstream
PLL has two or more output clocks.
17
Date Version Changes
May 2015 2015.05.04
• Added Arria V and Cyclone V devices in adjpllin Cascading for
Supported Devices table.
• cclk input clock source is not supported in Cyclone V devices.
Updated the information and notes in the following locations:
• Altera PLL IP Core Parameters - Cascading Tab table
• PLL-to-PLL Cascading section
• Reference Clock Inputs for Fractional PLL table
• Altera PLL Ports table
August 2014 2014.08.01
• Grouped parameters in separate tables according to parameter editor
tabs.
• Added parameters for the General tab and Cascading tab.
• Updated parameters for the Clock Switchover tab.
• Updated information on PLL-to-PLL Cascading.
• Added information on PLL output counter cascading.
December
1.3 Updated Table 3 on page 10 to update reset port information.
2013
(8)
Not supported in Cyclone V devices.
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Document Revision History
Date Version Changes
UG-01087
2015.05.04
March 2013 1.2
• Added the “Reference Clock Switchover” section.
• Added the “PLL to PLL Cascading” section.
• Added new parameters for the following features: clock switchover,
PLL cascading, MIF streaming, and PLL settings, in Table 1.
• Added the following new ports: refclk1, extswitch, activeclk, clkbad,
cclk, adjpilin, and cascade_out, in Table 3 and Figure 3.
January 2011 1.1
• Added two new parameters in Table 1.
• Updated Figure 3: ALTERA PLL Ports.
July 2010 1.0 Initial release.
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Altera Phase-Locked Loop (Altera PLL) IP Core User Guide
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