Arria® V Device Handbook: Volume 2: Transceivers

ID 683573
Date 5/29/2020
Public
Document Table of Contents

2.1. Input Reference Clocking

The reference clock for the transmitter PLL and CDR generates the clocks required for transceiver operation.
Table 37.  Input Reference Clock Sources
Sources Transmitter PLL CDR Jitter Performance 11
ATX PLL 12 CMU PLL > 6.5536 Gbps 13 CMU PLL <= 6.5536 Gbps fPLL
Dedicated refclk pin Yes Yes Yes Yes Yes 1
REFCLK network Yes Yes Yes Yes Yes 2
Dual-purpose RX/REFCLK pin Yes No 14 Yes Yes Yes 3
Fractional PLL Yes 15 Yes Yes Yes Yes 4
Generic CLK pin No No No No No 5
Core clock network (GCLK, RCLK, PCLK) No No No No No 6
Figure 40. Dedicated refclk Pin and Reference Clock NetworkThe following figure shows the dedicated refclk pin connection to channel PLL. The direct refclk pin connection to channel PLL (which can either be configured as CMU PLL or CDR) is only available in channel 1 and 4 in a bank.


Figure 41. Dedicated refclk Pin and Reference Clock Network for Arria V GZ Devices


Note: ATX PLL is available only for Arria V GZ devices.
Figure 42. Input Reference Clock Source for CMU PLL Driving Channels with Serial Data Rates Beyond 6.5536 Gbps


Table 38.  Electrical Specifications for the Input Reference Clock for Arria V GZ Devices
Protocol I/O Standard Coupling Termination
PCI Express (PCIe)
  • 1.2V PCML, 1.4 PCML
  • 1.4V PCML
  • 1.5V PCML
  • 2.5V PCML
  • Differential LVPECL
  • LVDS
AC On - Chip 16
DC Off - Chip 18
All other protocols
  • 1.2V PCML, 1.4 PCML
  • 1.4V PCML
  • 1.5V PCML
  • 2.5V PCML
  • Differential LVPECL
  • LVDS
AC On - Chip 16
Note: If you select the HCSL I/O standard for the PCIe reference clock, add the following assignment to your project's Quartus settings file (.qsf):
set_instance_assignment -name XCVR_REFCLK_PIN_TERMINATION_DC_COUPLING_EXTERNAL_RESISTOR -to <refclk_pin_name>
Figure 43. Termination Scheme for a Reference Clock Signal When Configured as HCSL for Arria V GZ Devices


Note:
  • No biasing is required if the reference clock signals are generated from a clock source that conforms to the PCIe specification.
  • Select Rs and / or Rp resistor values as recommended by the PCIe clock source vendor.
11 The lower number indicates better jitter performance.
12 ATX PLL is available only in Arria V GZ devices.
13 Applicable for 10 Gbps channels only in GT and ST devices and for 12.5 Gbps channels in GZ devices. For better jitter performance, use dedicated refclk pins for data rates > 6.5536 Gbps.
14 For Arria V GZ devices, the dual-purpose RX/REFCLK pin can be used as a reference clock source for CMU PLL with data rates > 6.5536 Gbps.
15 fPLL to ATX PLL cascading is only enabled for SDI applications
16 For more information about termination values supported, refer to the DC Characteristics section in Arria V Device Datasheet.
17 In PCIe mode, you have the option of selecting the HCSL standard for the reference clock if compliance to the PCIe protocol is required. You can select this I/O standard option only if you have configured the transceiver in PCIe mode.
18 For an example termination scheme refer to Figure 43