Altera Corporation
2–113
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
If you use the byte deserializer, the byte ordering might be different than
what you intended.
Figure 2–90
shows the byte deserializer operating in
single-width mode. The expected data pattern is A at the lower byte,
followed by B at the upper byte. C and D follow in the next lower and
upper bytes, respectively.
Figure 2–90. Intended Transmitter Pattern
The receiver may receive the intended transmitter pattern or slip a byte,
as shown in
Figure 2–91
, where A arrives when the byte deserializer is
stuffing the upper byte instead of stuffing the lower byte. This is a
nondeterministic swap, because it depends on PLL lock times and link
delay.
Figure 2–91. Incorrect Byte Position at Receiver After Byte Deserializer
You can use the byte ordering block or a byte reordering circuit to restore
the byte order to the expected pattern.
Byte Ordering
The Stratix II GX device has a dedicated byte ordering circuit on each
receiver to obtain a certain byte order on multiple lanes. This circuit is
used in conjunction with the byte deserializer block. The byte deserializer
doubles the number of lanes for each receiver. If you use the single-width
mode, the receiver output at the PLD interface 8-bits or 10-bits (single
lane) if the byte deserializer is not used, and 16-bit or 20-bit (dual lanes)
if it is used. If you use double-width mode, the receiver’s output at the
PLD interface is 16-bits or 20-bits (dual lanes) or 36-bits or 40-bits
(transceiver block lanes) if the byte deserializer is used. The nature of the
byte deserializer block does not lend itself to preserving the lane striping
of the source transmitter. The least significant byte of the transmitter may
be received in a different location. Refer to
“Byte Deserializer” on
page 2–112
for more details on how the bytes can be re-ordered. The byte
ordering block ensures that the correct lane striping is kept at the receiver
output.
X
B
D
X
A
C
A
C
X
X
B
D
Содержание Stratix II GX
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