Altera Corporation
2–183
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
The receiver outputs a K28.4 (
8'h9c + rx_ctrldetect
) at the
rx_dataout
port and de-asserts the
rx_syncstatus
(1'b0) signal
when the receiver is not synchronized. Once synchronized, the receiver
asserts the
rx_syncstatus
signal (1'b1). This signal is aligned with the
first valid data received from the
rx_dataout
port.
Figure 2–132
shows the receiver synchronization waveform. The
rx_syncstatus
port goes high when synchronization is complete,
indicating that the data is valid. In
Figure 2–132
, D1 is the first valid data.
Figure 2–132. Synchronization Complete
The receiver remains synchronized until it detects a string of bad code
groups or is reset. A bad code group is defined by the IEEE 802.3 standard
as four invalid code groups separated by less than three valid code
groups. If the receiver detects a bad code group or is reset, the
rx_syncstatus
signal goes high, then low and a /K28.4/ appears on
the
rx_outrx_dataout
port.
Idle Generation
In GIGE mode, any /Dx.y/ following a /K28.5/ comma is replaced by
the transmitter with either a /D5.6/ (8'hc5) or a /D16.2/ (8'h50)
depending on the current running disparity, except when the data
following the /K28.5/ is /D21.5/ (8'hb5) or /D2.2/ (8'h42). This ensures
the generation of the /I1/ (/K28.5/, /D5.6/) and /I2/ (/K28.5/,
/D16.2/) ordered sets and to allows the configuration ordered sets /C1/
(/K28.5, /D21.5/) and /C2/ (/K28.5/, /D2.2/) to be received. If the
running disparity before the idle ordered set is positive, a /I1/ is chosen.
If the running disparity is negative, an /I2/ is chosen. The disparity at the
end of an /I1/ is the opposite of that at the beginning of the /I1/. The
disparity at the end of an /I2/ is the same as the beginning running
disparity (right before the idle code). This ensures a negative running
disparity at the end of an idle ordered set. A /Kx.y/ following a /K28.5/
is not replaced.
clock
rx_dataout[7..0]
rx_syncstatus
xx
xx
xx
D1
D2
D3
D4
D5