Cyclone V Device Handbook: Volume 2: Transceivers

ID 683586
Date 10/24/2018
Public
Document Table of Contents

1.3.2.1.5. Word Aligner in Automatic Synchronization State Machine Mode with a 10-Bit PMA-PCS Interface Configuration

Protocols such as PCIe require the receiver PCS logic to implement a synchronization state machine to provide hysteresis during link synchronization. Each of these protocols defines a specific number of synchronization code groups that the link must receive to acquire synchronization and a specific number of erroneous code groups that it must receive to fall out of synchronization.

In PCIe configurations, the word aligner in automatic synchronization state machine mode automatically selects the word alignment pattern length and pattern as specified by each protocol. The synchronization state machine parameters are fixed for PCIe configurations as specified by the respective protocol.

Table 22.  Word Aligner in Synchronization State Machine Modes for a PCIe Configuration
Mode PCIe
Number of valid synchronization code groups or ordered sets received to achieve synchronization 4
Number of erroneous code groups received to lose synchronization 17
Number of continuous good code groups received to reduce the error count by one 16

After deassertion of the reset_rx_digital signal in automatic synchronization state machine mode, the word aligner starts looking for the word alignment pattern or synchronization code groups in the received data stream. When the programmed number of valid synchronization code groups or ordered sets is received, the rx_syncstatus status bit is driven high to indicate that synchronization is acquired. The rx_syncstatus status bit is constantly driven high until the programmed number of erroneous code groups is received without receiving intermediate good groups; after which rx_syncstatus is driven low. The word aligner indicates loss of synchronization (rx_syncstatus remains low) until the programmed number of valid synchronization code groups are received again.