Altera Stratix GX Transceiver - Manual (Page 85)

Altera Corporation 4–3
January 2005 Stratix GX Transceiver User Guide
SONET Mode
embedded word alignment circuit to use in conjunction with the pattern
detector to align the word boundary of the re-timed data to a specified
comma. In SONET mode, this embedded circuit is configured to manual
alignment mode consisting of 16-bit and bit-slip modes.
The word aligner is composed of a pattern detector, manual alignment
controller, bit-slipper circuitry, and synchronization state machines.
Depending on the configuration, these components work in conjunction
with or independently of one another. The word aligner cannot be
bypassed, but if the rx_enacdet signal is held low, the word aligner
does not alter the word boundary.
Figure 4–3 shows the various
components of the word aligner in SONET mode. The functionality is
described in the following sections.
Figure 4–3. Stratix GX Word Aligner Components
Pattern Detector Module
The pattern detector matches the comma to the current byte-boundary, as
specified in the MegaWizard
® Plug-In Manager. If the comma is found,
the optional rx_patterndetect signal is asserted for the duration of
one clock cycle to signify that the comma exists in the current word
boundary. The pattern detector module only indicates that the signal
exists and does not modify the word boundary. Modification of the word
boundary is discussed later in the word alignment and synchronization
sections.
Bit-slip
Mode
A1A2
Mode
SONET
Mode
A1A2
Mode
Word Aligner
Manual
Alignment Mode
A1A1A2A2
Mode
A1A1A2A2
Mode
Pattern
Detector
SONET
Mode