Arria® V Device Handbook: Volume 2: Transceivers

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ID 683573
Date 5/29/2020
Public
Document Table of Contents
Document Table of Contents x
1. Transceiver Architecture in Arria V Devices 2. Transceiver Clocking in Arria V Devices 3. Transceiver Reset Control in Arria V Devices 4. Transceiver Protocol Configurations in Arria V Devices 5. Transceiver Custom Configurations in Arria V Devices 6. Transceiver Configurations in Arria V GZ Devices 7. Transceiver Loopback Support in Arria V Devices 8. Dynamic Reconfiguration in Arria V Devices
1. Transceiver Architecture in Arria V Devices x
1.1. Architecture Overview 1.2. PCS Architecture 1.3. Channel Bonding 1.4. PLL Sharing 1.5. Document Revision History
1.1. Architecture Overview x
1.1.1. Transceiver Banks 1.1.2. 10-Gbps Support Capability in GT and ST Devices 1.1.3. Transceiver Channel Architecture 1.1.4. PMA Architecture
1.1.2. 10-Gbps Support Capability in GT and ST Devices x
1.1.2.1. Enhanced Small Form-Factor Pluggable (SFP+) Interface 1.1.2.2. 10GBASE-KR Support 1.1.2.3. 9.8 Gbps CPRI Application
1.1.4. PMA Architecture x
1.1.4.1. Transmitter PMA Datapath 1.1.4.2. Receiver PMA Datapath 1.1.4.3. Transmitter PLL 1.1.4.4. Clock Divider 1.1.4.5. Calibration Block
1.1.4.1. Transmitter PMA Datapath x
1.1.4.1.1. Serializer 1.1.4.1.2. Transmitter Buffer
1.1.4.2. Receiver PMA Datapath x
1.1.4.2.1. Receiver Buffer 1.1.4.2.2. Channel PLL 1.1.4.2.3. Deserializer
1.1.4.3. Transmitter PLL x
1.1.4.3.1. Auxiliary Transmit (ATX) PLL Architecture 1.1.4.3.2. CMU PLL 1.1.4.3.3. fPLL as Transmitter PLL
1.1.4.5. Calibration Block x
1.1.4.5.1. Offset Cancellation in the Receiver Buffer and Receiver CDR 1.1.4.5.2. ATX PLL Calibration for Arria V GZ Devices 1.1.4.5.3. Calibration Block Boundary
1.2. PCS Architecture x
1.2.1. Transmitter PCS Datapath for Arria V GX, SX, GT, and ST Devices and Arria V GZ Standard PCS 1.2.2. Receiver PCS Datapath for Arria V GX, SX, GT, and ST Devices and Arria V GZ Standard PCS 1.2.3. 10G PCS Architecture for Arria V GZ Devices 1.2.4. PCIe Gen3 PCS Architecture
1.2.1. Transmitter PCS Datapath for Arria V GX, SX, GT, and ST Devices and Arria V GZ Standard PCS x
1.2.1.1. Transmitter Phase Compensation FIFO 1.2.1.2. Byte Serializer 1.2.1.3. 8B/10B Encoder 1.2.1.4. Transmitter Bit-Slip
1.2.1.1. Transmitter Phase Compensation FIFO x
1.2.1.1.1. Phase Compensation Mode 1.2.1.1.2. Registered Mode
1.2.1.3. 8B/10B Encoder x
1.2.1.3.1. 8B/10B Encoder in Single-Width Mode 1.2.1.3.2. 8B/10B Encoder in Double-Width Mode 1.2.1.3.3. Running Disparity Control 1.2.1.3.4. Encoder Output During Reset Sequence
1.2.2. Receiver PCS Datapath for Arria V GX, SX, GT, and ST Devices and Arria V GZ Standard PCS x
1.2.2.1. Word Aligner 1.2.2.2. Rate Match FIFO 1.2.2.3. 8B/10B Decoder 1.2.2.4. Byte Deserializer 1.2.2.5. Byte Ordering 1.2.2.6. Receiver Phase Compensation FIFO
1.2.2.1. Word Aligner x
1.2.2.1.1. Word Aligner in Manual Alignment Mode 1.2.2.1.2. Bit-Slip Mode 1.2.2.1.3. Word Aligner in Automatic Synchronization State Machine Mode 1.2.2.1.4. Word Aligner in Deterministic Latency State Machine Mode 1.2.2.1.5. Programmable Run-Length Violation Detection 1.2.2.1.6. Receiver Polarity Inversion 1.2.2.1.7. Bit Reversal 1.2.2.1.8. Receiver Byte Reversal
1.2.2.3. 8B/10B Decoder x
1.2.2.3.1. 8B/10B Decoder in Single-Width Mode 1.2.2.3.2. 8B/10B Decoder in Double-Width Mode
1.2.2.5. Byte Ordering x
1.2.2.5.1. Byte Ordering in Single-Width Mode 1.2.2.5.2. Byte Ordering in Double-Width Mode 1.2.2.5.3. Word Aligner-Based Ordering Mode 1.2.2.5.4. Manual Ordering Mode
1.2.2.6. Receiver Phase Compensation FIFO x
1.2.2.6.1. Phase Compensation Mode 1.2.2.6.2. Registered Mode
1.2.3. 10G PCS Architecture for Arria V GZ Devices x
1.2.3.1. Transmitter 10G PCS Datapath 1.2.3.2. Receiver 10G PCS Datapath
1.2.3.1. Transmitter 10G PCS Datapath x
1.2.3.1.1. Transmitter FIFO 1.2.3.1.2. Frame Generator 1.2.3.1.3. CRC-32 Generator 1.2.3.1.4. 64B/66B Encoder 1.2.3.1.5. Scrambler 1.2.3.1.6. Disparity Generator 1.2.3.1.7. Transmitter Gearbox
1.2.3.2. Receiver 10G PCS Datapath x
1.2.3.2.1. Receiver Gearbox 1.2.3.2.2. Block Synchronizer 1.2.3.2.3. Disparity Checker 1.2.3.2.4. Descrambler 1.2.3.2.5. Frame Synchronizer 1.2.3.2.6. Bit-Error Rate (BER) Monitor 1.2.3.2.7. 64B/66B Decoder 1.2.3.2.8. CRC-32 Checker 1.2.3.2.9. Receiver FIFO
1.2.4. PCIe Gen3 PCS Architecture x
1.2.4.1. Transmitter PCIe Gen3 PCS Datapath 1.2.4.2. Receiver PCIe Gen3 PCS Datapath 1.2.4.3. PIPE Interface
1.2.4.1. Transmitter PCIe Gen3 PCS Datapath x
1.2.4.1.1. Phase Compensation FIFO (Shared with Standard PCS) 1.2.4.1.2. Scrambler 1.2.4.1.3. Encoder 1.2.4.1.4. Gearbox
1.2.4.2. Receiver PCIe Gen3 PCS Datapath x
1.2.4.2.1. Block Sync 1.2.4.2.2. Rate Match FIFO 1.2.4.2.3. Decoder 1.2.4.2.4. Descrambler
1.2.4.3. PIPE Interface x
1.2.4.3.1. Auto Speed Negotiation Block 1.2.4.3.2. Electrical Idle Inference Block 1.2.4.3.3. Clock Data Recovery (CDR) Control Block
1.3. Channel Bonding x
1.3.1. Bonded Channel Configurations 1.3.2. Non-Bonded Channel Configurations
2. Transceiver Clocking in Arria V Devices x
2.1. Input Reference Clocking 2.2. Internal Clocking 2.3. FPGA Fabric–Transceiver Interface Clocking 2.4. Document Revision History
2.1. Input Reference Clocking x
2.1.1. Reference Clock Network 2.1.2. Dual-Purpose RX/refclk Pin 2.1.3. Fractional PLL (fPLL)
2.2. Internal Clocking x
2.2.1. Transmitter Clock Network 2.2.2. Transmitter Clocking 2.2.3. Receiver Clocking
2.2.2. Transmitter Clocking x
2.2.2.1. Non-Bonded Channel Configurations 2.2.2.2. Bonded Channel Configurations
2.2.3. Receiver Clocking x
2.2.3.1. Receiver Non-Bonded Channel Configurations 2.2.3.2. Receiver Bonded Channel Configurations
2.3. FPGA Fabric–Transceiver Interface Clocking x
2.3.1. Transceiver Datapath Interface Clocking 2.3.2. Transmitter Datapath Interface Clocking 2.3.3. Receiver Datapath Interface Clock 2.3.4. GXB 0 PPM Core Clock Assignment for GZ Devices
2.3.2. Transmitter Datapath Interface Clocking x
2.3.2.1. Quartus II-Software Selected Transmitter Datapath Interface Clock 2.3.2.2. Selecting a Transmitter Datapath Interface Clock
2.3.3. Receiver Datapath Interface Clock x
2.3.3.1. Quartus II Software-Selected Receiver Datapath Interface Clock 2.3.3.2. Selecting a Receiver Datapath Interface Clock
3. Transceiver Reset Control in Arria V Devices x
3.1. PHY IP Embedded Reset Controller 3.2. User-Coded Reset Controller 3.3. Transceiver Reset Using Avalon Memory Map Registers 3.4. Clock Data Recovery in Manual Lock Mode Resetting the Transceiver During Dynamic Reconfiguration 3.6. Transceiver Blocks Affected by the Reset and Powerdown Signals 3.7. Transceiver Power-Down 3.8. Document Revision History
3.1. PHY IP Embedded Reset Controller x
3.1.1. Embedded Reset Controller Signals 3.1.2. Resetting the Transceiver with the PHY IP Embedded Reset Controller During Device Power-Up 3.1.3. Resetting the Transceiver with the PHY IP Embedded Reset Controller During Device Operation
3.2. User-Coded Reset Controller x
3.2.1. User-Coded Reset Controller Signals 3.2.2. Resetting the Transmitter with the User-Coded Reset Controller During Device Power-Up 3.2.3. Resetting the Transmitter with the User-Coded Reset Controller During Device Operation 3.2.4. Resetting the Receiver with the User-Coded Reset Controller During Device Power-Up Configuration 3.2.5. Resetting the Receiver with the User-Coded Reset Controller During Device Operation
3.3. Transceiver Reset Using Avalon Memory Map Registers x
3.3.1. Transceiver Reset Control Signals Using Avalon Memory Map Registers
3.4. Clock Data Recovery in Manual Lock Mode x
3.4.1. Control Settings for CDR Manual Lock Mode 3.4.2. Resetting the Transceiver in CDR Manual Lock Mode
4. Transceiver Protocol Configurations in Arria V Devices x
4.1. PCI Express 4.2. Gigabit Ethernet 4.3. XAUI 4.4. 10GBASE-R 4.5. Serial Digital Interface 4.6. Gigabit-Capable Passive Optical Network (GPON) 4.7. Serial Data Converter (SDC) JESD204 4.8. SATA and SAS Protocols 4.9. Deterministic Latency Protocols—CPRI and OBSAI 4.10. Serial RapidIO 4.11. Document Revision History
4.1. PCI Express x
4.1.1. PCIe Transceiver Datapath 4.1.2. PCIe Supported Features 4.1.3. PIPE Transceiver Channel Placement Guidelines 4.1.4. PCIe Supported Configurations and Placement Guidelines 4.1.5. PIPE Transceiver Clocking
4.1.2. PCIe Supported Features x
4.1.2.1. PIPE Interface 4.1.2.2. Transmitter Electrical Idle Generation 4.1.2.3. Power State Management 4.1.2.4. 8B/10B Encoder Usage for Compliance Pattern Transmission Support 4.1.2.5. Receiver Status 4.1.2.6. Receiver Detection 4.1.2.7. Clock Rate Compensation Up to ±300 ppm 4.1.2.8. PCIe Reverse Parallel Loopback
4.2. Gigabit Ethernet x
4.2.1. Gigabit Ethernet Transceiver Datapath
4.3. XAUI x
4.3.1. Transceiver Datapath in a XAUI Configuration 4.3.2. XAUI Supported Features 4.3.3. Transceiver Clocking and Channel Placement Guidelines in XAUI Configuration
4.4. 10GBASE-R x
4.4.1. 10GBASE-R Transceiver Datapath Configuration 4.4.2. 10GBASE-R Supported Features 4.4.3. 10GBASE-R Transceiver Clocking
4.5. Serial Digital Interface x
4.5.1. Configurations Supported in SDI Mode 4.5.2. Serial Digital Interface Transceiver Datapath
4.9. Deterministic Latency Protocols—CPRI and OBSAI x
4.9.1. Latency Uncertainty Removal with the Phase Compensation FIFO in Register Mode 4.9.2. Channel PLL Feedback for Deterministic Relationship 4.9.3. CPRI and OBSAI 4.9.4. CPRI Enhancements
5. Transceiver Custom Configurations in Arria V Devices x
5.1. Standard PCS Configuration 5.2. Standard PCS in Low Latency Configuration 5.3. PMA Direct 5.4. Document Revision History
5.1. Standard PCS Configuration x
5.1.1. Custom Configuration Channel Options 5.1.2. Rate Match FIFO in Custom Configuration
5.1.2. Rate Match FIFO in Custom Configuration x
5.1.2.1. Rate Match FIFO Behaviors in Custom Single-Width Mode 5.1.2.2. Rate Match FIFO Behaviors in Custom Double-Width Mode
5.2. Standard PCS in Low Latency Configuration x
5.2.1. Low Latency Custom Configuration Channel Options
6. Transceiver Configurations in Arria V GZ Devices x
6.1. 10GBASE-R and 10GBASE-KR 6.2. Interlaken 6.3. PCI Express (PCIe)—Gen1, Gen2, and Gen3 6.4. XAUI 6.5. CPRI and OBSAI—Deterministic Latency Protocols 6.6. Transceiver Configurations 6.7. Native PHY IP Configuration 6.8. Document Revision History
6.1. 10GBASE-R and 10GBASE-KR x
6.1.1. 10GBASE-R and 10GBASE-KR Transceiver Datapath Configuration 6.1.2. 10GBASE-R and 10GBASE-KR Supported Features 6.1.3. 1000BASE-X and 1000BASE-KX Transceiver Datapath 6.1.4. 1000BASE-X and 1000BASE-KX Supported Features 6.1.5. Synchronization State Machine Parameters in 1000BASE-X and 1000BASE-KX Configurations 6.1.6. Transceiver Clocking in 10GBASE-R, 10GBASE-KR, 1000BASE-X, and 1000BASE-KX Configurations
6.2. Interlaken x
6.2.1. Transceiver Datapath Configuration 6.2.2. Supported Features 6.2.3. Transceiver Clocking
6.3. PCI Express (PCIe)—Gen1, Gen2, and Gen3 x
6.3.1. Transceiver Datapath Configuration 6.3.2. Supported Features for PCIe Configurations PIPE 2.0 Interface Dynamic Switching Between Gen1 (2.5 Gbps) and Gen2 (5 Gbps) Signal Rates Transmitter Electrical Idle Generation Power State Management 8B/10B Encoder Usage for Compliance Pattern Transmission Support Receiver Electrical Idle Inference Receiver Status Receiver Detection Gen1 and Gen2 Rate Match FIFO PCIe Reverse Parallel Loopback 6.3.3. Supported Features for PCIe Gen3 6.3.4. Transceiver Clocking and Channel Placement Guidelines 6.3.5. Advanced Channel Placement Guidelines for PIPE Configurations 6.3.6. Transceiver Clocking for PCIe Gen3
6.4. XAUI x
6.4.1. Transceiver Datapath in a XAUI Configuration 6.4.2. Supported Features 6.4.3. Transceiver Clocking and Channel Placement Guidelines
6.5. CPRI and OBSAI—Deterministic Latency Protocols x
6.5.1. Transceiver Datapath Configuration 6.5.2. Phase Compensation FIFO in Register Mode 6.5.3. Channel PLL Feedback 6.5.4. CPRI and OBSAI
6.6. Transceiver Configurations x
6.6.1. Standard PCS Configurations—Custom Datapath 6.6.2. Standard PCS Configurations—Low Latency Datapath 6.6.3. Transceiver Channel Placement Guidelines 6.6.4. 10G PCS Configurations 6.6.5. Merging Instances
6.6.4. 10G PCS Configurations x
6.6.4.1. 10G PCS Datapath Functionality 6.6.4.2. Using the coreclkin Ports
6.7. Native PHY IP Configuration x
6.7.1. Protocols and Transceiver PHY IP Support 6.7.2. Native PHY Transceiver Datapath Configuration 6.7.3. Standard PCS Features 6.7.4. 10G PCS Supported Features 6.7.5. 10G Datapath Configurations with Native PHY IP 6.7.6. PMA Direct Supported Features 6.7.7. Channel and PCS Datapath Dynamic Switching Reconfiguration
6.7.3. Standard PCS Features x
6.7.3.1. Standard PCS Receiver and Transmitter Blocks
6.7.4. 10G PCS Supported Features x
6.7.4.1. 10G PCS Receiver and Transmitter Blocks 6.7.4.2. Receiver and Transmit Gearbox in Native PHY IP
7. Transceiver Loopback Support in Arria V Devices x
7.1. Serial Loopback 7.2. Forward Parallel Loopback 7.3. PIPE Reverse Parallel Loopback 7.4. Reverse Serial Loopback 7.5. Reverse Serial Pre-CDR Loopback 7.6. Document Revision History
8. Dynamic Reconfiguration in Arria V Devices x
8.1. Dynamic Reconfiguration Features 8.2. Offset Cancellation 8.3. Transmitter Duty Cycle Distortion Calibration 8.4. PMA Analog Controls Reconfiguration 8.5. Dynamic Reconfiguration of Loopback Modes 8.6. Transceiver PLL Reconfiguration 8.7. Transceiver Channel Reconfiguration 8.8. Transceiver Interface Reconfiguration 8.9. Reduced .mif Reconfiguration 8.10. On-Chip Signal Quality Monitoring (Eye Viewer) 8.11. Adaptive Equalization 8.12. Decision Feedback Equalization 8.13. Unsupported Reconfiguration Modes 8.14. Document Revision History
1. Transceiver Architecture in Arria V Devices
2. Transceiver Clocking in Arria V Devices
3. Transceiver Reset Control in Arria V Devices
4. Transceiver Protocol Configurations in Arria V Devices
5. Transceiver Custom Configurations in Arria V Devices
6. Transceiver Configurations in Arria V GZ Devices
7. Transceiver Loopback Support in Arria V Devices
8. Dynamic Reconfiguration in Arria V Devices

6.3.2. Supported Features for PCIe Configurations

The features supported for a PCIe configuration are different for the 2.5 Gbps, 5 Gbps, and 8 Gbps data rate configurations.
Table 78.  Supported Features for PCIe Configurations
Feature

Gen1

(2.5 Gbps)

Gen2

(5 Gbps)

Gen3

(8 Gbps)

x1, x2, x4, x8 link configurations Yes Yes Yes
PCIe-compliant synchronization state machine Yes Yes Yes
±300 ppm (total 600 ppm) clock rate compensation Yes Yes Yes
8-bit FPGA fabric-transceiver interface (PIPE 2.0) Yes — —
16-bit FPGA fabric-transceiver interface (PIPE 2.0) Yes Yes —
32-bit FPGA fabric-transceiver interface (PIPE 3.0-like) — — Yes
64-bit Hard IP Avalon-ST interface width (Hard IP only) Yes Yes Yes
128-bit Hard IP Avalon-ST interface width (Hard IP only) Yes Yes Yes
256-bit Hard IP Avalon-ST interface width (Hard IP only) — Yes Yes
Transmitter driver electrical idle Yes Yes Yes
Receiver Detection Yes Yes Yes
8B/10B encoder/decoder disparity control Yes Yes —
128B/130B encoder/decoder — — Yes
Power state management Yes Yes Yes
Receiver PIPE status encoding ( pipe_rxstatus[2:0] ) Yes Yes Yes
Dynamic switching between 2.5 Gbps and 5 Gbps signaling rate — Yes —
Dynamic switching between 2.5 Gbps, 5 Gbps, and 8 Gbps signaling rate — — Yes
Dynamic transmitter margining for differential output voltage control — Yes Yes
Dynamic transmitter buffer de-emphasis of -3.5 dB and -6 dB — Yes Yes
Dynamic Gen3 transceiver pre-emphasis, de-emphasis, and equalization — — Yes

PIPE 2.0 Interface

In a PCIe PIPE configuration, each channel has a PIPE interface block that transfers data, control, and status signals between the PHY-MAC layer and the transceiver channel PCS and PMA blocks. The PIPE configuration complies with the PIPE 2.0 specification. If you use a PIPE configuration, you must implement the PHY-MAC layer using soft IP in the FPGA fabric.

Besides transferring data, control, and status signals between the PHY-MAC layer and the transceiver, the PIPE interface block implements the following functions required in a PCIe-compliant physical layer device:

  • Forcing the transmitter driver into the electrical idle state
  • Initiating the receiver detect sequence
  • Controlling the 8B/10B encoder/decoder
  • Controlling the 128B/130B encoder/decoder
  • Managing the PCIe power states
  • Indicating the completion of various PHY functions
  • Encoding the receiver status and error conditions on the pipe_rxstatus[2:0] signal, conforming to the PCIe PIPE 3.0 specification

Transceiver datapath clocking varies between non-bonded (x1) and bonded (x2, x4, and x8) configurations.

Dynamic Switching Between Gen1 (2.5 Gbps) and Gen2 (5 Gbps) Signal Rates

In a PIPE configuration, the PIPE Parameter Editor provides an input signal (pipe_rate) that is functionally equivalent to the RATE signal specified in the PCIe specification. A low-to-high transition on this input signal (pipe_rate) initiates a data rate switch from Gen1 to Gen2. A high-to-low transition on the input signal initiates a data rate switch from Gen2 to Gen1. The signaling rate switch between Gen1 and Gen2 is achieved by changing the transceiver datapath clock frequency between 250 MHz and 500 MHz, while maintaining a constant, 16-bit width transceiver interface.

Transmitter Electrical Idle Generation

The PIPE interface block in Arria V GZ devices puts the transmitter buffer in the channel in an electrical idle state when the electrical idle input signal is asserted. During electrical idle, the transmitter buffer differential and common configuration output voltage levels are compliant to the PCIe Base Specification 2.0 for both PCIe Gen1 and Gen2 data rates.

The PCIe specification requires the transmitter driver to be in electrical idle in certain power states. For more information about input signal levels required in different power states, refer to “Power State Management”.

Power State Management

The PCIe specification defines four power states—P0, P0s, P1, and P2—that the physical layer device must support to minimize power consumption:

  • P0 is the normal operating state during which packet data is transferred on the PCIe link.
  • P0s, P1, and P2 are low-power states into which the physical layer must transition as directed by the PHY-MAC layer to minimize power consumption.

The PIPE interface in Arria V GZ transceivers provides an input port for each transceiver channel configured in a PIPE configuration.

Note: When transitioning from the P0 power state to lower power states (P0s, P1, and P2), the PCIe specification requires the physical layer device to implement power saving measures. Arria V GZ transceivers do not implement these power saving measures except for putting the transmitter buffer in electrical idle in the lower power states.

8B/10B Encoder Usage for Compliance Pattern Transmission Support

The PCIe transmitter transmits a compliance pattern when the Link Training and Status State Machine (LTSSM) enters the Polling.Compliance substate. The Polling.Compliance substate is used to assess if the transmitter is electrically compliant with the PCIe voltage and timing specifications.

Receiver Electrical Idle Inference

The PCIe protocol allows inferring the electrical idle condition at the receiver instead of detecting the electrical idle condition with analog circuitry.

In all PIPE configurations, (x1, x2, x4, and x8), each receiver channel PCS has an optional Electrical Idle Inference module that implements the electrical idle inference conditions specified in the PCIe Base Specification 2.0.

Receiver Status

The PCIe specification requires the PHY to encode the receiver status on a 3-bit status signal (pipe_rxstatus[2:0]). This status signal is used by the PHY-MAC layer for its operation. The PIPE interface block receives status signals from the transceiver channel PCS and PMA blocks, and encodes the status on the pipe_rxstatus[2:0] signal to the FPGA fabric. The encoding of the status signals on the pipe_rxstatus[2:0] signal conforms to the PCIe specification.

Receiver Detection

The PIPE interface block in Arria V GZ transceivers provides an input signal (pipe_txdetectrx_loopback) for the receiver detect operation required by the PCIe protocol during the Detect state of the LTSSM. When the pipe_txdetectrx_loopback signal is asserted in the P1 power state, the PCIe interface block sends a command signal to the transmitter driver in that channel to initiate a receiver detect sequence. In the P1 power state, the transmitter buffer must always be in the electrical idle state. After receiving this command signal, the receiver detect circuitry creates a step voltage at the output of the transmitter buffer. If an active receiver (that complies with the PCIe input impedance requirements) is present at the far end, the time constant of the step voltage on the trace is higher when compared with the time constant of the step voltage when the receiver is not present. The receiver detect circuitry monitors the time constant of the step signal seen on the trace to determine if a receiver was detected. The receiver detect circuitry requires a 125-MHz clock for operation that you must drive on the fixedclk port.

Note: For the receiver detect circuitry to function reliably, the transceiver on-chip termination must be used and the AC-coupling capacitor on the serial link and the receiver termination values used in your system must be compliant with the PCIe Base Specification 2.0.

The PIPE core provides a 1-bit PHY status (pipe_phystatus) and a 3-bit receiver status signal (pipe_rxstatus[2:0]) to indicate whether a receiver was detected or not, as per the PIPE 2.0 specifications.

Gen1 and Gen2 Rate Match FIFO

In compliance with the PCIe protocol, Arria V GZ receiver channels have a rate match FIFO to compensate for small clock frequency differences up to ±300 ppm between the upstream transmitter and the local receiver clocks.

PCIe Reverse Parallel Loopback

PCIe reverse parallel loopback is only available in a PCIe functional configuration for Gen1, Gen2, and Gen3 data rates. The received serial data passes through the receiver CDR, deserializer, word aligner, and rate matching FIFO buffer. The data is then looped back to the transmitter serializer and transmitted out through the transmitter buffer. The received data is also available to the FPGA fabric through the port. This loopback mode is compliant with the PCIe specification 2.0. Arria V GZ devices provide an input signal to enable this loopback mode.

Note: This is the only loopback option supported in PIPE configurations.
Figure 171. PCIe Reverse Parallel Loopback Mode DatapathThe grayed-out blocks are Inactive.


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