Altera Corporation
2–109
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Figure 2–86. 20-Bit to 16-Bit Conversion
Code Error detect
The
rx_errdetect
signal indicates when a code received contains an
error. This port is optional but, if not in use, there is no way to detect if the
code received is valid or not. The
rx_errdetect
signal goes high if a
code received is an invalid code or if it has a disparity error. If a code is
received that is not part of the valid Dx.y or Kx.y list, the
rx_errdetect
signal goes high. This signal is aligned to the invalid code word received
at the PLD logic array.
In double-width mode, the
rx_errdetect
signal is 2-bits wide in the
PCS portion of the transceiver. The lower bit indicates if the LSByte
contains a code error, the upper bit indicates if the MSByte contains a code
error. The value of the invalid code can vary and should be ignored.
Disparity Error Detector
The 8B/10B decoder in double-width mode forwards the current running
disparity value from the LSByte decoder to the MSByte decoder to check
the disparity of the symbol going into the MSByte decoder. The MSByte
decoder’s ending running disparity is then fed back to the LSByte
decoder on the next clock cycle.
f
Refer to the
Specifications & Additional Information
chapter in volume 2 of
the
Stratix II GX Device Handbook
for information on the disparity
calculation.
19
18
17
16
15
14
13
12
11
10
Cascaded 8B/10B Conversion
j
1
h
1
g
1
f
1
i
1
e
1
d
1
c
1
b
1
a
1
MSB
LSB
15
14
13
13
11
10
9
8
H
1
G
1
F
1
E
1
D
1
C
1
B
1
A
1
CTRL[1..0]
9
8
7
6
5
4
3
2
1
0
j
h
g
f
i
e
d
c
b
a
7
6
5
4
3
2
1
0
H
G
F
E
D
C
B
A
Parallel Data
Содержание Stratix II GX
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