Microsemi AC483 PolarFire FPGA Transceiver Signal Integrity User Guide
- June 9, 2024
- Microsemi
Table of Contents
AC483 Polarize FPGA Transceiver Signal Integrity
User Guide
AC483
Application Note
Polar Fire FPGA Transceiver Signal Integrity
AC483 Polar Fire FPGA Transceiver Signal Integrity
Micro semi makes no warranty, representation, or guarantee regarding the
information contained herein or the suitability of its products and services
for any particular purpose, nor does Micro semi assume any liability
whatsoever arising out of the application or use of any product or circuit.
The products sold hereunder and any other products sold by Micro semi have
been subject to limited testing and should not be used in conjunction with
mission-critical equipment or applications. Any performance specifications
are believed to be reliable but are not verified, and Buyer must conduct and
complete all performance and other testing of the products, alone and together
with, or installed in, any end-products. Buyer shall not rely on any data and
performance specifications or parameters provided by Micro semi. It is the
Buyer’s responsibility to independently determine suitability of any products
and to test and verify the same. The information provided by Micro semi
hereunder is provided “as is, where is” and with all faults, and the entire
risk associated with such information is entirely with the Buyer. Micro semi
does not grant, explicitly or implicitly, to any party any patent rights,
licenses, or any other IP rights, whether with regard to such information
itself or anything described by such information. Information provided in this
document is proprietary to Micro semi, and Micro semi reserves the right to
make any changes to the information in this document or to any products and
services at any time without notice.
About Micro semi
Micro semi, a wholly owned subsidiary of Microchip Technology Inc. (Nasdaq:
MCHP), offers a comprehensive portfolio of semiconductor and system solutions
for aerospace & defense, communications, data center and industrial markets.
Products include high-performance and radiation-hardened analog mixed-signal
integrated circuits, FPGAs, SoCs and ASICs; power management products; timing
and synchronization devices and precise time solutions, setting the world’s
standard for time; voice processing devices; RF solutions; discrete
components; enterprise storage and communication solutions, security
technologies and scalable anti-tamper products; Ethernet solutions; Power-
over-Ethernet ICs and midspans; as well as custom design capabilities and
services. Learn more at www.microsemi.com.
Revision History
The revision history describes the changes that were implemented in the
document. The changes are listed by revision, starting with the current
publication.
1.1 Revision 2.0
• Added Enhanced Receiver Management options in Libero Flow, page 16.
• Added new Rx CTLE settings, see Table 5, page 13.
1.2 Revision 1.0
The first publication of this document.
Transceiver Tuning
This document describes the several Polar Fire Transceiver signal integrity
settings as well as IBIS-AMI and Smart Debug features.
The document covers the design flow required to perform successful signal
integrity tuning at both
Transmitter (Tx) and Receiver (Rx) end. For commonly used terminologies, see
Glossary, page 23.
Transceiver tuning for Polar Fire devices is done three different ways:
-
Traditional Method (Non-simulation flow): Traditional method is based on learnings developed from experience. If costumers know the channel loss, then based on the recommendations provided in this document or on the basis of users experiences, Transceiver attributes are loaded to the device. This method does not guarantee the ideal Transceiver performance.
-
IBIS-AMI Simulations: Transceiver tuning based on IBIS-AMI Simulations is the best method available. Simulations helps to build confidence on the performance of the hardware. In simulations, both the transmitter and receiver variables can be changed and output is observed. This method provides a clear image on how the different Transceiver attributes impacts the performance of the system. The appropriate Transceiver attributes obtained from the simulation can be applied to the device by two ways:
-
Through Libero: Change the attributes in the design while generating the bit file.
-
Through Smart Debug: The Smart Debug tool provides the facility to vary between the multiple attributes using the same bit file.
Detailed explanation of tuning using IBIS-AMI Simulations is provided in this document. -
Smart Debug: Smart Debug is used for debugging the Transceiver using electrical parameters such as Tx amplitude, De-emphasis, driver impedance, Rx impedance, CTLE and DFE calibration. It gives freedom to the users to play with the signal integrity settings based on the simulations or intuitions. Details of Smart Debug are discussed in the later section of this document. For more information, see Smart Debug User Guide for Polar Fire FPGAs.
Note: Receiver optimization is disabled in Libero SoC v12.0 Smart Debug. It will be fixed in a future version.
Polar Fire transceivers have a memory mapped Dynamic Reconfiguration Interface (DRI) which allows Smart Debug to communicate with the transceiver blocks in real- time. This feature provides debugging capabilities and altering of the transceivers for optimized performance in the system. After the final Smart Debug signal integrity optimization, the user can export the tuned information back into the Libero SoC software for future design regeneration.
Figure 1 • Transceiver Signal Integrity Tuning Flow
2.1 Transmitter
High speed transmitter has following capabilities that user can adjust to make
the system work. Note that only transmitter tuning alone does not help for
high loss channel, receiver tuning is also required to make system work
without errors.
- Amplitude: Transmitter supports 10 amplitude settings from 100mV to 1000mV in steps of 100mV.
- De-emphasis: Transmitter supports six de-emphasis settings. Those are 0dB, -1dB, -2.5dB, -3.5dB,-4.4dB and -6dBmV.
- Termination impedance: Transmitter supports four driver terminations. Those are 85 Ω, 100 Ω,150 Ω and 180 Ω.
- Jitter: In the IBIS-AMI simulation, the following Jitter parameters can be used for the transmitter:
- TX (Tx Duty cycle Distortion)
- TX (Tx Deterministic Jitter)
- TX (Tx Random Jitter)
Note: See Polar Fire IBIS-AMI Models for the worst-case jitter numbers. By default, these jitter numbers are considered while running IBIS-AMI simulations.
The following table describes the recommended Tx settings for different channel lengths.
Table 1 • Recommended Driver Amplitude, De-emphasis, Impedance Settings
Amplitude and De-emphasis Setting (mV with dB)| Tx Termination (Ω)|
Recommended channel
---|---|---
100mV with 0dB| 100| Very Short
200mV with 0dB| 100| Very Short
200mV with -1dB| 100| Very Short
200mV with -2.5dB| 100| Very Short
200mV with -3.5dB| 100| Very Short
200mV with -4.4dB| 100| Very Short
200mV with -6dB| 100| Very Short
300mV with 0dB| 100| Short
400mV with 0dB| 100| Short
400mV with -1dB| 100| Short
400mV with -2.5dB| 100| Short
400mV with -3.5dB| 100| Short
400mV with -4.4dB| 100| Short
400mV with -6dB| 100| Short
500mV with 0dB| 100| Short
600mV with -3.5dB| 150| Short/Medium
600mV with -6dB| 150| Short/Medium
800mV with 0dB| 150| Short/Medium/Long
800mV with -1dB| 150| Short/Medium/Long
800mV with -2.5dB| 150| Short/Medium/Long
800mV with -3.5dB| 150| Short/Medium/Long
800mV with -4.4dB| 150| Short/Medium/Long
800mV with -6dB| 150| Short/Medium/Long
1000mV with 0dB| 180| Short/Medium/Long
1000mV with -1dB| 180| Short/Medium/Long
Amplitude and De-emphasis Setting (mV with dB)| Tx Termination (Ω)|
Recommended channel
---|---|---
1000mV with -2.5dB| 180| Short/Medium/Long
1000mV with -3.5dB| 180| Short/Medium/Long
1000mV with -4.4dB| 180| Short/Medium/Long
1000mV with -6dB| 180| Short/Medium/Long
Note: Apart from these recommended settings, each driver termination (85,100,150 and 180 Ω) has 29 amplitude and emphasis settings ranging from 100mV with 0dB to 1000mV with -6dB. User can apply any of the recommended or other settings to the silicon according to their applications.
2.1.1 IBIS-AMI
The Tx parameters are accessed in the IBIS-AMI simulation in the following
ways:
- Amplitude and De-emphasis is through the variable Amphorae.
- Driver Termination is the through selecting the appropriate pin in the IBIS as listed in the following table.
Table 2 • Tx Model Pin Description
Pin | Variable Name | Description |
---|---|---|
5, 6 | microsemi_pf_100_tx | 100 to 1000mV with 100 Ω termination |
11, 12 | microsemi_pf_150_400tx | 100 to 400mV with 150 Ω termination |
13, 14 | microsemi_pf_150_800tx | 600 to 800mV with 150 Ω termination |
7, 8 | microsemi_pf_150_tx | 1000mV with 150 Ω termination |
15, 16 | microsemi_pf_180_400tx | 100 to 400mV with 180 Ω termination |
17, 18 | microsemi_pf_180_800tx | 600 to 800mV with 180 Ω termination |
9, 10 | microsemi_pf_180_tx | 1000mV with 180 Ω termination |
3, 4 | microsemi_pf_85_tx | 100 to 1000mV with 85 Ω termination |
The PolarFire IBIS-AMI models can be downloaded from link
https://www.microsemi.com/products/fpgasoc/design-resources/ibis-models/ibis-
models-polarfire.
The following table shows the IBIS-AMI model files contained in the model
package files and its descriptions.
Table 3 • IBIS-AMI Model File Description
File Name | Description |
---|---|
microsemi_pf_spisim.ibs | Top-level IBIS models and wrappers for Tx and Rx AMI |
model.
MPF300T-TX-R085.ami| All Amplitude and de-emphasis settings with 85 0
termination, full set of settings are present in this transmitter AMI model.
MPF300T-TX-R100.ami| All Amplitude and de-emphasis settings with 100 0
termination, full set of settings are present in this transmitter AMI model.
MPF300T-TX-R150.ami| 1000mv amplitude settings with 150 0 termination
MPF300T-TX-R150_800.ami| 800mv and 600mv amplitude settings with 150 0
termination
MPF300T-TX-R150_400.ami| 100mv to 500mv amplitude settings with 150 0
termination
MPF300T-TX-R180.ami| 1000mv amplitude settings with 180 0 termination
MPF300T-TX-R180_800.ami| 800mv and 600mv amplitude settings with 180 0
termination
MPF300T-TX-R180_400.ami| 100mv to 500mv amplitude settings with 180 0
termination
2.1.2 Libero Flow
The Tx and Rx settings obtained from IBIS-AMI simulation can be directly
applied to the device through Libero. In this section, settings related to Tx
are discussed. Following are the steps to apply Tx signal integrity settings.
To create the transceiver based design:
- Run the Synthesize, this enables the Manage Constraints
- Go to Manage Constraints
- Go to I/O Attributes
- Select the Target
- Click Edit > Edit with I/O Editor as show in the following figure
After the I/O Editor is opened, perform the following steps:
- Select XCVR View tab.
- Select the appropriate lane.
- Go to Signal Integrity View present in the right bottom as shown in the following figure.
- Set the Tx settings such as, Amplitude with de-emphasis, Tx Impedance as shown in the following figure.
XCVR view tab provides options to apply different Tx settings and
Termination impedance. Select the appropriate settings and apply. After this
step, both Tx and Rx settings are applied to Transceiver.
This fixes the Tx and Rx settings into staple (bit file) file. In-order to
debug the design with respect to signal integrity, change the Tx and Rx
settings through Smart Debug on the fly.
2.1.3 Smart Debug Flow
When the design is not working as expected, Smart Debug is used to debug the
design with respect to signal integrity related issues. For more information
on Smart Debug, see Smart Debug User Guide for Polar Fire FPGAs.
For Tx, Smart Debug is used to change the settings such as amplitude, de-
emphasis and driver termination settings live on the hardware. There are two
ways the hardware can be debugged.
- Use existing design which sends data.
- Use in-built PRBS generator from Smart Debug.
Note: Only Tx settings are discussed in this section, however, for successful debug, both Tx and Rx need to be tuned. For Rx setting, see Receiver, page 11
Following steps describe the debugging of the design with respect to Tx.
-
Program the bit file (.step) on to the device.
-
Open the corresponding Libero Project.
-
Double click the Generate Smart Debug FPGA Array Data on Libero Software. Once the array data is generated, a green tick mark appears as shown in the following figure.
Figure 4 • Smart Debug FPGA Array Data -
After generating the data successfully open the Smart Debug Design from the Libero Design Flow.
Note that the Hardware has to be connected with Flash Pro programmer and power on. If the Smart Debug is opened without powering up the hardware, it opens up in Demo Mode. Connect the hardware using Flash Pro programmer and open the Smart Debug Design from the Libero Design Flow. It opens Smart Debug window as shown in the following figure. Click Debug Transceiver. -
Go to Smart BERT tab and select the required lane to assign the pattern and Transmitter attributes as shown in the following figure. Select any data pattern or the existing design sends the data pattern.
-
From the drop down menu select the Tx Emphasis amplitude. Selected option sets the device registers to provide the desired de-emphasis for the particular signal amplitude. Tx impedance is also decided based on the signal amplitude.
-
After all the step are completed, click Apply for new settings on the device.
-
The inbuilt PRBS generator can be used to send out the data pattern. To enable PRBS generator select appropriate PRBS pattern and click Start on the Smart Bert window as shown in the following figure.
2.1.4 Illustration
This section describes an example for testing the performance of IBIS-AMI
model using Polar Fire Evaluation Kit.
Device and Setup Details
- Device Used: MPF300T-1FCG1152.
- Transceiver block: Two Lane 0 is used for measurement.
- Dedicated internal reference clock is used for the SERDES block (156.25MHz).
- LVDS25 IO standard is used to reference clock input.
- 23GHz Tektronix (DPO72304) scope and 100G samples/sec setting is used for measuring jitter and plotting eye.
- Two feet long cable (part# Scolex 100 126E) is used for connecting the Tx ports to the scope.
- 2.3 inch long trace is connecting the device and the Tx SMA ports.
- Clock Recovery Configuration:- Method: PLL-Custom BW, PLL Model: Type II, Damping:700m In the measurement the appropriate Tx settings is loaded to the silicon through Smart Debug as explained in Smart Debug Flow, page 7.Use the inbuilt PRBS31 generator to send the data out. Following figure shows the hardware setup used for the measurement.Design used to test the transmitter performance of the IBIS-AMI model is shown in the following figure. With the help of sweep option different de-emphasis settings is tested and the one which provides the best result is then loaded to Smart Debug. Measurement result is obtained with the best suited settings which is correlated with the simulation to fine tune the model.
The IBIS-AMI Tx model is connected to pass through Rx model which is a simple
100 Ω termination through die parasitic, package, board and 24 inch cable
s-parameter model. The measurement environment is created virtually through
the design in ADS.
Parameter sweep option is used to test the 29 different de-emphasis setting
marked as 1 to 29 with each corresponding to a specific value of signal
amplitude and de-emphasis.
Figure 10, page 11 shows the correlation between measurement and IBIS-AMI
simulation for following settings:
- Tx Amplitude: 800 mV
- De-emphasis: 0 dB
- Tx Termination: 150 Ω
- Data Rate: 10.3125 Gbps
Simulated Tx Eye correlates well with measurement as shown in following figure.
Note: Blue represents Simulation and Red represents Measurement.
2.2 Receiver
High speed data coming from transmitter passing through a channel can result
in degradation of the signals and making it difficult for the receiver to
detect it correctly. As the data rate increases, equalization at the receiver
becomes a necessity. Equalizers are used to compensate the high frequency
losses included by the channel. Analog equalization is done by Continuous
Time Linear Equalizers (CTLE) whereas discrete time equalization can be
achieved by Decision Feedback Equalization (DFE). For lower data rates CTLE
is sufficient, however, for higher data rate DFE is also used along with CTLE.
Polar Fire Rx supports 85 Ω, 100 Ω and 150 Ω terminations. The Receiver
provides three types of equalizations as explained:
- CDR Mode: This option provides users to apply any CTLE setting including the recommended (Default values in the Libero) ones or settings obtained from the IBIS-AMI simulations.
- CDR Mode with Calibration : The device internal algorithm optimizes the receiver and applies the best CTLE settings in the device for the given channel and Tx attributes.
- DFE Mode: Polar Fire transceiver is built with a five tap DFE engine. DFE is used when the data rate is high or loss of the channel is too high. DFE is always used along with CTLE. In CDR Mode with calibration, the device optimizes the receiver and provides best CTLE and associated DFE coefficients. DFE in IBIS-AMI simulations is only used to sign-off the hardware.
For receiver tuning 63 CTLE settings are provided. Libero default CTLE settings are assigned for a particular data rate range and channel however other settings can also be used for the same range as shown in the following table.
Table 4 • Default Rx CTLE Settings
Insertion Loss | Data Rate (Mbps) | Mode | RX_CTLE Value |
---|---|---|---|
Short (6.5dB) | 250-5000 | CDR | No Peak +2.8 dB |
5000-6875 | CDR | 3 GHz +1.4 dB | |
6875-8437.5 | CDR | 5 GHz +1.8 dB | |
8437.5-10312.5 | CDR | 5 GHz +7.3 dB | |
10312.5-12700 | DFE | 5 GHz +10.6dB | |
Medium (17.0dB) | 250-5000 | CDR | 3 Ghz +5.5 dB |
5000-6875 | CDR | 3 GHz +1.4 dB | |
6875-8437.5 | DFE | 5 GHz +7.3 dB | |
8437.5-10312.5 | DFE | 5 GHz +7.3 dB | |
10312.5-12700 | DFE | 6 GHz +11.1dB | |
Long (25.0dB) | 250-5000 | CDR | 3 Ghz +11.4 dB |
5000-6875 | CDR | 3 GHz +6.8 dB | |
6875-8437.5 | DFE | 5 GHz +7.3 dB | |
8437.5-10312.5 | DFE | 5 GHz +7.3 dB | |
10312.5-12700 | DFE | 6 GHz +11.1dB |
The following table contains the information about all 63 CTLE settings and
the recommended data rate range in which they are used. Note that user can set
any settings for any data rate.
Table 5 • Rx CTLE Settings
S.No.| RX_CTLE Settings| DC Gain (dB)| Peak AC Gain (dB)|
Data Rate (Mbps)
---|---|---|---|---
1| NoPeak+7.3dB| 7.27| 7.28| 250 – 1600
2| NoPeak+9.3dB| 9.28| 9.29| 250 – 1600
3| NoPeak+2.8dB| 2.85| 3.07| 250 – 1600
4| 3Ghz+5.5dB| -2.28| 3.17| 250 – 1600
5| 3Ghz+11.4dB| -7.98| 3.46| 250 – 1600
6| NoPeak+2.82dB| 2.82| 2.84| 250 – 1600
7| NoPeak+0.1dB| 0.12| 0.13| 250 – 1600
8| NoPeak-2.5dB| -2.57| -2.48| 250 – 1600
9| NoPeak-7.1dB| -7.15| -6.86| 250 – 1600
10| 3GHz+4.62dB| -13.00| -8.38| 250 – 1600
11| NoPeak+4.6dB| 4.61| 4.62| 250 – 1600
12| NoPeak+1.8dB| 1.86| 1.88| 250 – 1600
13| NoPeak-0.9dB| -0.94| -0.87| 250 – 1600
14| NoPeak-5.6dB| -5.61| -5.42| 250 – 1600
15| 3GHz+4.6_dB| -11.60| -6.99| 250 – 1600
16| 3GHz+11.0dB| -9.34| 1.71| >1600 – 5000
17| 3GHz+5.6dB| -6.43| -0.77| >1600 – 5000
18| NoPeak-1.1dB| -1.17| -0.62| >1600 – 5000
19| 3GHz+12.3dB| -12.77| -0.44| >1600 – 5000
20| 3GHz+2.3_dB| -6.48| -4.18| >1600 – 5000
21| 3GHz+9.0dB| -12.96| -3.90| >1600 – 5000
22| 3GHz+5.9dB| -5.02| 0.90| >1600 – 5000
23| NoPeak+0.3dB| 0.37| 1.01| >1600 – 5000
24| 3GHz+12.6dB| -11.37| 1.24| >1600 – 5000
25| 3GHz+2.4dB| -5.07| -2.66| >1600 – 5000
26| 3GHz+9.1dB| -11.54| -2.37| >1600 – 5000
27| 3GHz+1.4dB| 4.55| 5.96| >5000 – 6875
28| 3GHz+6.8dB| -2.32| 4.53| >5000 – 6875
29| 3GHz+12.9dB| -8.07| 4.88| >5000 – 6875
30| 3GHz+7.8dB| -5.11| 2.70| >5000 – 6875
31| 3GHz+2.2dB| 0.29| 2.57| >5000 – 6875
32| 3GHz+14.5dB| -11.50| 3.05| >5000 – 6875
33| 3GHz+4.8dB| -5.16| -0.29| >5000 – 6875
34| 3GHz+11.8dB| -11.67| 0.17| >5000 – 6875
35| 5GHz+1.8dB| 4.56| 6.36| >6875 – 8437.5
36| 5GHz+7.3dB| -2.30| 5.03| >6875 – 8437.5
S.No.| RX_CTLE Settings| DC Gain (dB)| Peak AC Gain (dB)|
Data Rate (Mbps)
---|---|---|---|---
37| 5GHz+13.4dB| -8.07| 5.38| >6875 – 8437.5
38| 5GHz+8.4dB| -5.11| 3.33| >6875 – 8437.5
39| 5GHz+2.8dB| 0.30| 3.14| >6875 – 8437.5
40| 5GHz+15.1dB| -11.50| 3.68| >6875 – 8437.5
41| 5GHz+5.7dB| -5.16| 0.58| >6875 – 8437.5
42| 5GHz+12.7dB| -11.70| 1.09| >6875 – 8437.5
43| 5GHz+9.8dB| -5.43| 4.40| >8437.5 – 10312.5
44| 5GHz+12.4dB| -8.09| 4.35| >8437.5 – 10312.5
45| 5GHz+9.6dB| -5.40| 4.22| >8437.5 – 10312.5
46| 5GHz+10.6dB| -5.38| 5.20| >8437.5 – 10312.5
47| 6GHz+11.1dB| -4.34| 6.79| >10312.5
48| 6GHz+10.1dB| -4.34| 5.79| >10312.5
49| 6GHz+10.13dB| -4.18| 5.95| >10312.5
50| 6GHz+12.2dB| -10.14| 2.06| >10312.5
51| 6GHz+11.0dB| -6.82| 4.24| >10312.5
52| 6_GHz+12.0dB| -6.97| 5.07| >10312.5
53| 6GHz+11.5dB| -7.25| 4.28| >10312.5
54| 6GHz+13.1dB| -7.17| 5.92| >10312.5
55| NoPeak+9.22 dB| 9.22| 9.24| >8437.5 – 10312.5
56| NoPeak+4.53 dB| 4.53| 4.55| >8437.5 – 10312.5
57| NoPeak+1.76 dB| 1.76| 1.78| >8437.5 – 10312.5
58| 5GHz+3.14 dB| -1.52| 1.61| >8437.5 – 10312.5
59| NoPeak+11.10 dB| 11.10| 11.13| >10312.5
60| NoPeak+6.13 dB| 6.13| 6.15| >10312.5
61| NoPeak+3.39 dB| 3.39| 3.41| >10312.5
62| 6GHz+2.73 dB| 0.32| 3.06| >10312.5
63| 6GHz+3.12 dB| 1.50| 4.62| >10312.5
For higher dates rate, 5 tap DFE is used along with CTLE. Libero sets the
default DFE and CTLE settings for given channel and data rate as shown in
following table.
Note: These settings are used when auto calibration of DFE is not
selected.
Table 6 • Default Rx DFE Coefficients
Channel | Data Rate | Celt Setting | DFE Coefficients |
---|---|---|---|
SHORT | 10312.5-12700 | 5GHz+10.6dB | 6,-3,-2,-1,-1 |
MEDIUM | 6875 – 8437.5 | 5GHz+7.3dB | 7,1,2,2,0 |
MEDIUM | 8437.5 – 10312.5 | 5GHz+7.3dB | 8,-3,-2,-1,0 |
MEDIUM | 10312.5-12700 | 6GHz+11.1dB | 10,0,-2,-1,0 |
Channel | Data Rate | Ctle Setting | DFE Coefficients |
--- | --- | --- | --- |
LONG | 6875 – 8437.5 | 5GHz+7.3dB | 7,-1,0,0,0 |
LONG | 8437.5 – 10312.5 | 5GHz+7.3dB | 8,-5,-1,-1,0 |
LONG | 10312.5-12700 | 6GHz+11.1dB | 10,1,0,0,0 |
2.2.1 IBIS-AMI
This section describes the IBIS-AMI Rx model parameters that needs to be
varied in order to obtain proper tuning of the receiver. In Rx model, AMI tab
contains four important parameters used for receiver optimization. The
following table lists the information about the four key parameters.
Table 7 • Rx Model Parameter Descriptions
Rx Variable | Description |
---|---|
RXTERM | Rx Termination. It supports 85 Ω, 100 Ω and 150 Ω |
CTLE_ID | This parameter changes the CTLE Settings. Total 63 settings are |
provided. Detailed description of the complete 63 settings are provided in Tab
le 5, page 13.
DFE_MODE| Determine the DFE calibration mode.
1=off, 2=fixed, 3=adapt.
Adapt mode does auto calibration of the device to obtain the best DFE
coefficients where as in fixed mode coefficients are added manually.
DFE_TAP| 5 Tap DFE is used.
Each tap can be manually edited by the costumers in DFE_MODE=2 or DFE_MODE=3.
In DFE_MODE=3 the tool takes the value provided in DFE_TAP as initial values
to obtain the optimized DFE coefficients.
DFE, when used in adapt mode, calibrates the receiver and gives the best DFE
coefficients. These coefficients are then used in the fixed mode in simulation
to view the proper eye. Each DFE coefficient in Libero corresponds to 6m in
IBIS-AMI DFE tap (tap1 to tap5). Mapping of the coefficients is described in
the following table.
Table 8 • DFE Coefficient Mapping between IBIS-AMI and Libero
IBIS AMI Value| Libero Value (Hex)| IBIS AMI Value|
Libero Value (Hex)
---|---|---|---
0.006| -1| -0.006| 1
0.012| -2| -0.012| 2
0.018| -3| -0.018| 3
0.024| -4| -0.024| 4
0.03| -5| -0.03| 5
0.036| -6| -0.036| 6
0.042| -7| -0.042| 7
0.048| -8| -0.048| 8
0.054| -9| -0.054| 9
0.06| -a| -0.06| a
0.066| -b| -0.066| b
0.72| -c| -0.72| c
0.78| -d| -0.78| d
Table 8 • DFE Coefficient Mapping between IBIS-AMI and Libero
IBIS AMI Value| Libero Value (Hex)| IBIS AMI Value|
Libero Value (Hex)
---|---|---|---
0.084| -e| -0.084| e
0.09| -f| -0.09| f
2.2.2 Libero Flow
Transceiver settings applied using Libero while generating the bit file is
explained in IBIS-AMI, page 5. Apart from the earlier explained settings, the
Rx model has an additional option for receiver calibration. This feature is
available only in Libero SoC 12.0 and above and not supported by Libero
version 2.3 or below.
Select the Transceiver Interface in the Smart Design window to open the
configurator dialog box as shown in following figure. The Transceiver supports
Enhanced Receiver Management (ERM), which adds DFE/CDR calibration management
and lock-to-data detection capabilities. The ERM is implemented in the FPGA
logic inside the XCVR component. For more information about ERM, see the
Enhanced Receiver Management section in Polar Fire and Polar Fire SoC FPGA
Transceiver User Guide.
The following receiver calibration options are provided for the ERM operation:
- None (CDR): Select this option if the XCVR is configured as CDR and no CTLE auto-calibration is performed. Static settings are configured by Libero SoC based on data rate and backplane model.
- On-Demand: Select this option to perform calibration on-demand. This option is available for both CDR and DFE configuration of the XCVR. You can trigger calibration on-demand using CALIB_REQ port as shown in Figure 12, page 17. The CALIBRATING signal is asserted upon CALIB_REQ assertion and de-asserted when the calibration is completed.
- On-Demand and First Lock: This method is an extension to On-Demand calibration option. This allows the customers to perform CDR/DFE calibration either by toggling the CALIB_REQ pin or after the power on reset.
- None (DEF): DC Offset Calibration of the CDR is performed, however, the DFE Coefficients are set through PDC commands used from the register rather than from automatic DFE calibration operation. To set the required registers with static values, users must enhance the “section” PDC command to add new attributes. The new attributes that need to be added are highlighted in the following example PDC file.
section -port_name LANE0_RXD_N \
-RX_DFE_COEFFICIENT_H1 20 \
-RX_DFE_COEFFICIENT_H2 20 \
-RX_DFE_COEFFICIENT_H3 20 \
-RX_DFE_COEFFICIENT_H4 20 \
-RX_DFE_COEFFICIENT_H5 20 \
-DIRECTION INPUT
The RX_DFE_COEFFICIENT attributes are optional (applied only when Static calibration is selected). These attributes take integer values between 0 and 15. The corresponding register fields are 5 bits wide in all cases with the MSB bit reserved for sign bit. DEF does not use the DFE calibration routine and requires the user to carefully select DFE coefficient values. These values can be gathered by the Smart Debug tool or by simulation. When an initial calibration is completed, the performance of the DFE path can be improved incrementally in the following ways.
- Incrementally Recalibrate Data Eye: This recalibration should improve the data eye for most gradients that typically occur from temperature or voltage changes within the system.
- Incrementally Recalibrate DFE Coefficient: This recalibration performs the DFE calibration in incremental method. The initially calculated DFE coefficient values are used as the starting values for this algorithm.This results in the reduction of the Calibration time by reducing the number of DFE coefficients that requires recalibration.
Note: Full calibration is always done for DFE. You must select any one of
the two options—On-Demand and First Lock or On-Demand—if the transceiver is
configured in DFE mode.
In the Signal Integrity View window of I/O Editor shown in Figure 3, page
6, the following Rx settings are selected.
- Calibration: None(CDR)/On-Demand/On-Demand and First lock/None(Static DFE) options are provided. Please refer receiver calibration modes described above.
- RX_CTLE : 63 CTLE settings are provided as shown in Table 5, page 13. Users can select any value from IBIS-AMI simulations or recommended values from Ta bleb 4, page 12 or from Table 5, page 13.
- DFE Mod e: DFE mode is enabled automatically based on the data rate and insertion loss of a channel. DFE values are either auto-tuned in On-demand/On-demand and First Lock mode or set to values recommended in Table 4, page 12 or set by PDC commands in static DFE mode described in the previous section.
2.2.3 Smart Debug Flow
Follow the section Smart Debug Flow, page 7 for invoking the Smart Debug GUI
from the Libero. Select the appropriate receiver settings from the menu as
shown in following figure. Click Apply to apply the settings to Polar Fire
transceiver.
CTLE mode: user can select any of 63 CTLE settings from Rx CTLE tab.
After selecting the Transmitter and Receiver attributes.
DFE mode: in case the design working in DFE mode, use Optimize Receiver
button to auto tune the CTLE and DFE settings. New settings will be displays
on the GUI.
In case, user using far end loop back mode, user can generate the PRBS pattern
to transfer the data stream. Click Start to start the data out as shown in the
Figure 13, page 18.
2.2.4 Illustration
For receiver performance of the IBIS-AMI model, the following design is used
as shown in Figure 14, page 19. The Tx is connected to the Rx through, board,
24 inch cables, package and backplane. The output of the backplane is looped
back the Polar Fire Evaluation kit Rx SMAs. Following figure shows the
hardware setup.
The equivalent IBIS-AMI simulation setup is shown in the following figure.
The different modes are described as follows.
2.2.4.1 CTLE (CDR mode)
CTLE can be used up to 10.3125 Gbps for short channel as shown in the Table 4,
page 12. The following example show the data capture with default Libero
settings as well as optimal CTLE values from IBISAMI simulations at
10.3125Gbps. The system used for the short reach is 5 inch backplane channel
along with cables and Polar Fire board traces with following transceiver
settings.
-
Tx: 400mV, 0dB, 100 Ω
-
Rx: 100 Ω
Libero default CTLE: 5GHz+7.3db and CTLE from Simulation: 5GHz+1.8db -
Data Pattern: PRBS31
The following figure shows the eye Plot from Simulation with Libero default CTLE setting and corresponding eye from ye monitor on Smart Debug
The following figure shows eye plot captured with optimal CTLE setting from Simulation and corresponding eye from eye monitor on Smart Debug.
Note that, eye with simulated CTLE values look better than the Libero default
CTLE setting since the Libero default CTLE setting is calibrated to have loss
of 6.5dB which is higher than the loss used in this example. Default Libero
settings works with zero bit error however, best value can be found from the
IBIS-AMI simulation. In case of CDR Mode with calibration, Transceiver tunes
the best CTLE setting.
CTLE can be used up to 6.8Gbps for long channel as shown in the table 4. Below
example show the data capture with default Libero settings as well as optimal
CTLE values from IBIS-AMI simulations at 6.25Gbps. The system used for the
long reach is 34 inch backplane channel along with cables and Polar Fire board
traces.
-
Tx: 1000mV, -6dB, 180 Ω
-
Rx: 100 Ω
Libero default CTLE: 3GHz+6.8db
CTLE from Simulation: 5GHz+7.3db -
Data Pattern: PRBS31
The following figure shows the eye from simulation with Libero default CTLE setting and Corresponding Eye from Eye Monitor on Smart Debug
The following figure shows eye captured with optimal CTLE setting from simulation and corresponding eye from eye monitor on Smart Debug.
Both the eyes with Libero default CTLE and CTLE from simulation shows similar results.
2.2.4.2 DFE Mode
DFE is used above 6.8Gbps for long and medium reach channel, and above
10.3125Gbps for short reach channel. Below example is based on long channel at
12.5Gbps. The transceiver tunes the best value with following system
attributes.
- Channel: 34 inch backplane channel and 4 inch Polar Fire Evaluation Kit PCB trace
- Tx Amplitude: 800 mV
- De-emphasis: 0 dB
- Tx Termination: 150 Ω
- Data Rate: 12.5 Gbps
- Data pattern: PRBS31
Following figure shows the eye obtained in Smart Debug. The system works with zero bit errors.![Microsemi AC483 PolarFire FPGA Transceiver Signal Integrity
- Backplane](https://manuals.plus/wp-content/uploads/2023/03/Microsemi-AC483 -PolarFire-FPGA-Transceiver-Signal-Integrity-Backplane.png)The blue portion shows the zero bit error rate region.
Glossary
Following are the commonly used terminology in this document.
- TX: Transmitter
- RX: Receiver
- Channel: The connecting medium between Transceiver TX to Transceiver RX is called channel. A channel may contains PCB traces, connectors, cables and backplanes.
- Insertion Loss: The Insertion loss is the loss of signal power resulting from the insertion due to a transmission line (Channel) and is usually expressed in decibels. The insertion loss is always expressed with respect to frequency. In this document, the loss is expressed at 5Ghz frequency.
- Reach: Reach is a way express the insertion loss of the channel in simple terms. The following terms are used in the document
- Very Short Channel or Very Short Reach: channel loss is less than 2dB
- Short length Channel or Short Reach: channel loss is less than 6.5dB
- Medium length Channel or Medium Reach: channel loss is less than 17dB
- Long length Channel or Long Reach: channel loss is less than 25dB
- Libero: Libero is a software to design and generate the Polarize FPGA programming bit file.
- Smart Debug: A tool in the Libero used for debugging the transceiver online.
- IBIS-AMI: IBIS-AMI is a set of files used to simulate the Polarize transceiver with channel, using simulators such as ADS, Hyperlinks, Systems, QCD and so on. IBIS- AMI simulations helps in finalizing the transceiver settings and sign-off its hardware.
Microchip Proprietary
References
- Microsemi | Semiconductor & System Solutions | Power Matters
- Microchip Lightning Support
- Multiple Results
- Empowering Innovation | Microchip Technology
- Microsemi | Semiconductor & System Solutions | Power Matters
- Microsemi | Microsemi