Altera Stratix GX Transceiver User Manual
Page 160
6–6
Altera Corporation
Stratix GX Transceiver User Guide
January 2005
GigE Mode Receiver Architecture
In GigE mode, the MegaWizard
®
Plug-In Manager defaults to the 10-bit
/K28.5/
code as the comma character. The Quartus
®
II software
automatically sets the options related to the word aligner, and you cannot
change these options in GigE mode. This 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 you specify a /K28.5/ (b’0011111010) pattern as the
comma, the rx_patterndetect signal asserts if either the
b’0011111010
or b’1100000101 pattern is present in the incoming
data.
To use transceiver parameters to set the functional mode, you must
preconfigure the receiver with a K28.5 (10’b0101111100 or
10’b1010000011
) word align pattern (ALIGN_PATTERN =
0101111100
or ALIGN_PATTERN = 1010000011). Set the
ALIGN_PATTERN_LENGTH
to 10, even though a 7-bit comma string
(7’b0011111 as a comma- or 7’b1100000 as a comma+) is allowed, as
stated in the IEEE 802.3 specification. This 7-bit comma is part of the
/K28.1/
, /K28.5/, and /K28.7/ code-groups. Use a 10-bit /K28.5/
code group to prevent a 7-bit comma from being detected across
boundaries when a /K28.7/ code is followed by a /K28.x/, /D3.x/,
/D11.x/
, /D12.x/, /D19.x/, /D20.x/, or /D28.x/ code group,
where x is a value from 0 to 7.
shows this situation.
Figure 6–5. A Cross-boundary 7-bit Comma When a /K28.7/ Code is Followed by a /K28.5/ Code
The receiver sends a K28.4 (8’h9c + rx_ctrldetect) code from the
rx_out[]
port and deasserts the rx_syncstatus (1’b0) signal when
the receiver is not synchronized. When synchronized, the receiver asserts
the rx_syncstatus (1’b1) signal. This signal is aligned with the first
valid data received from the rx_out[] port.
shows the waveforms related to receiver synchronization. The
rx_syncstatus
signal goes high when synchronization is complete,
indicating that the data is valid. In the example, D1 is the first valid data.
1
1
1
1
1
0
0
0
0
0
7-bit comma-
K28.7
1
1
1
1
1
0
1
0
0
0
7-bit comma+
K28.5