Altera Stratix GX Transceiver User Manual
Page 50
3–4
Altera Corporation
Stratix GX Transceiver User Guide
January 2005
Basic Mode Receiver Architecture
A 10-bit pattern, 7-bit pattern, or 16-bit pattern can be programmed for
the pattern detector to recognize. Refer to the section
MegaWizard Plug-In” on page 3–29
for more details.
10-Bit Pattern Mode
When the word alignment pattern length parameter in the MegaWizard
®
Plug-In Manager is set to 10, the module matches the 10-bit comma with
the data and its complement in the current word boundary. Both positive
and negative disparities are checked in this mode. For example, if a
/K28.5/
(b'0011111010) pattern is specified as the comma, the
rx_patterndetect
is asserted if b'0011111010 or b'1100000101 is
detected in the incoming data.
7-Bit Pattern Mode
When the word alignment pattern length parameter in the MegaWizard
Plug-In Manager is set to 7, the module matches the 7-bit comma
specified in the wizard field parameter with the seven least significant
bits (LSB) of the data and its complement in the current word boundary.
Both positive and negative disparities are also checked in this mode.
The 7-bit pattern mode is useful because it can mask out the three most
significant bits of the data. This lets the pattern detector recognize
multiple commas. For example, in the 8b/10b encoded data, a /K28.5/
(b'0011111010)
, /K28.1/ (b'0011111001), and /K28.7/
(b'0011111000)
shares seven common LSBs, so masking the three
MSBs lets the pattern detector resolve all three commas.
16-Bit Pattern Mode
The two consecutive 8-bit characters (A1A2) are used as the comma in
16-bit pattern mode.
A1
represents the least significant byte, which consists of bits [7..0],
and A2 represents the most significant byte, consisting of bits [15..8].
Therefore, the comma must be specified as [A2,A1] in the MegaWizard
Plug-In Manager word alignment comma section. Only the positive
disparity of the comma is detected in the mode. The A1A1A2A2 mode is
only available when SONET is specified as the protocol.
Table 3–1. Pattern Detector Comma Patterns in Basic Mode
Pattern Detect Mode
Data Width
Disparity
10-bit
10-bits, 20-bits
±
7-bit 10-bits,
20-bits
±
Two consecutive 8-bit characters
8-bits, 16-bits
+