Opal Kelly Blog

SYZYGY Specification 1.1 Release

The latest version of the SYZYGY specification has a few minor updates as well as the addition of a new port type. Here’s everything to know about the new release:

Introducing TXR-4

We have been working with one of the SYZYGY adopters to add a new four-lane transceiver specification. This new peripheral and port combination enables support for a wider range of off-the-shelf transceiver peripherals. We wanted to avoid any additional splintering of the specification in such a way that it would be difficult for carriers or peripherals to consistently support SYZYGY. This is a challenge when considering FPGA hardware interconnect that supports such an enormous array of peripherals.

After much debate, we decided that a new TXR-4 peripheral type was likely inevitable and would be better to add this device family earlier rather than later when more carrier and peripherals are supported and, therefore, incompatible with the new port type.

Here’s what the old TXR-2 (left) and new TXR-4 (right) connections look like (differences are highlighted in yellow):

The changes comprise:

  • Normal FPGA I/O signals S10-S17 are removed.
  • A second transceiver pair has been added where S10-S17 are on the TXR-2.


TXR-4 peripherals must have “1.1” configured as their required DNA version. If a TXR-4 peripheral is connected to a carrier at a TXR-2 location, the carrier must not power the corresponding VIO group.

A new attribute flag (IS_TXR4) has been added so that carriers can identify a TXR-4 peripheral and determine compatibility accordingly.

Firmware Updates

The XEM7320 and SYZYGY Brain-1 firmwares have been updated to support recognition of DNA version 1.1 and TXR-4 peripherals. Note that TXR-4 peripherals are not compatible with these carriers.

These firmware updates also include enforcement of the DNA required version.

Hardware Support

The current versions of the XEM7320 and Brain-1 support TXR-2 peripherals and do not support TXR-4 peripherals. It is planned to update this in future releases of these products.

New Peripheral Requirements

The SYZYGY specification now requires that all peripherals keep output (peripheral to carrier) signals at 0 V or in a high-impedance state until the VIO supply is enabled. Failure of a peripheral to meet this requirement could result in damage to a carrier due to back-powering a supply rail through an unpowered FPGA bank.


The updated specifications may be found online at the SYZYGY Specification page.

The syzygy-tools Github repository has been updated with support for the new DNA specification.

The XEM7320 firmware update is available through the FrontPanel firmware update wizard.

An updated SD card image for the Brain-1 is available through the Brain-1 attachments on Aligni. This update enforces support of the “required version” portion of the SYZYGY DNA specification and will not power a properly-configured TXR-4 peripheral.