Altera RapidIO II MegaCore Function - Manual (Page 118)

4–76 Chapter 4: Functional Description
Error Detection and Management
RapidIO II MegaCore Function August 2014 Altera Corporation
User Guide
To meet the RapidIO specification requirements for packet priority handling and
deadlock avoidance, the Physical layer transmitter includes four transmit queues and
four retransmit queues, one for each priority level.
The transmit buffer is the main memory in which the packets are stored before they
are transmitted. The buffer is partitioned into 64-byte blocks to be used on a
first-come, first-served basis by the transmit and retransmit queues.
The following events cause any stored packets to be lost:
■ Fatal error caused by receiving a link-response control symbol with the
port_status
set to OK but the ackid_status set to an ackID that is not pending
(transmitted but not acknowledged yet).
■ Fatal error caused by transmitter timing out while waiting for link-response.
■ Fatal error caused by receiver timing out while waiting for link-request.
■ Receive four consecutive link-request control symbols with the cmd set to
reset-device
.
Error Detection and Management
The error detection and management mechanisms in the RapidIO specification and
those built into the RapidIO II IP core provide a high degree of reliability. In addition
to error detection, management, and recovery features, the RapidIO II IP core also
provides debugging and diagnostic aids. The RapidIO II IP core optionally
implements the Error Management Extensions block and registers.
This section describes the error detection and management features in the RapidIO II
IP core.
Physical Layer Error Management
Most errors at the Physical layer are in one of the following two categories:
■ Protocol violations
■ Transmission errors
Protocol violations can be caused by a link partner that is not fully compliant to the
specification, or can be a side effect of the link partner being reset.
Transmission errors can be caused by noise on the line and consist of one or more bit
errors. The following mechanisms exist for checking and detecting errors:
■ The receiver checks the validity of the received 8B10B encoded characters,
including the running disparity.
■ The receiver detects control characters changed into data characters or data
characters changed into control characters, based on the context in which the
character is received.
■ The receiver checks the CRC of the received control symbols and packets.