Metastability detector and calibration method for synchronous data transfer

A method for calibrating a distributed synchronous system comprising a first transceiver device with a first transceiver digital sub-system connected to a second transceiver device with a second transceiver digital sub-system via an external connection, the method comprising:

• generating a toggle sequence with a clock phase and a 50% duty cycle in a pattern generator in the first transceiver digital sub-system, and transmitting a signal containing the toggle sequence to the second transceiver device;
• receiving the signal in the second transceiver device, and synchronizing to a signal pattern in the received signal and resulting from the toggle sequence, with a synchronizer device in the second transceiver digital sub-system to provide a re-synchronized signal pattern;
• incrementing an interval counter when the re-synchronized signal pattern is equal to 1 and decrementing the interval counter when the re-synchronized signal pattern is equal to 0 for a logic level interval of the re-synchronized signal pattern;
• accumulating an absolute value of the interval counter at an end of the logic level interval and providing a metastability value based on the accumulated absolute value;
• evaluating whether the metastability value is zero;
• determining a reference clock phase correlated with the metastability value of zero;
• and
• adjusting the clock phase of a signal for data transfer from the first transceiver device to the second transceiver device based on the reference clock phase.

A distributed synchronous system comprising:

• a first transceiver device with a first transceiver digital sub-system;
• and
• a second transceiver device connected to the first transceiver device, wherein:
• the second transceiver device includes a second transceiver digital sub-system via an external connection;
• the first transceiver digital sub-system includes a pattern generator for generating a toggle sequence with a clock phase and a 50% duty cycle;
• and
• the first transceiver digital sub-system is configured to generate subsequent toggle sequences with different clock phases;
• and
• the second transceiver digital sub-system includes:
• a synchronizer device configured to receive a signal pattern present in a received signal and resulting from a toggle sequence generated in the first transceiver device, and to produce a re-synchronized signal pattern by re-synchronization to the received signal pattern;
• and
• a metastability detector device to provide a metastability value of the re-synchronized signal pattern indicative of a degree of metastability of the re-synchronized signal pattern,
• wherein the metastability detector device includes at least one metastability detector, or
• wherein the distributed synchronous system is configured to perform, before or between transferring data, a calibration method for obtaining synchronized data transfer between the first transceiver device and the second transceiver device.

A method for transferring reliable high-speed data in a distributed synchronous system comprising a first transceiver device with a first transceiver digital sub-system connected to a second transceiver device with a second transceiver digital sub-system via an external connection, the method comprising:

• implementing, at the second transceiver digital sub-system, a metastability detector device configured to detect metastability events resulting from clock phase misalignment, the metastability detector device comprising at least one metastability detector;
• providing, at the first transceiver device, a pattern generator for generating a toggle sequence with a first clock phase and a 50% duty cycle, and configured to generate subsequent toggle sequences with a plurality of second clock phases;
• or
• performing, before use or in between data transfer operations, a calibration method;
• selecting a clock phase from the first clock phase or the plurality of second clock phases resulting in a metastability of zero for data transfer;
• and
• transferring data from the first transceiver device to the second transceiver device using the selected clock phase.