2–116
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Receiver Modules
Unlike word alignment based byte ordering, PLD-controlled byte
ordering does not require resetting the channel to re-trigger the byte
ordering process. A rising edge on the
rx_enabyteord
signal
re-triggers the process by de-asserting the
rx_byteorderalignstatus
signal. The byte ordering block starts
looking for the byte ordering pattern again and adds pad bytes as
necessary to achieve byte ordering. Once it completes the byte ordering
process, it asserts the
rx_byteorderalignstatus
signal.
Figure 2–95
shows PLD-controlled byte ordering in Basic double-width
Mode.
Figure 2–95. User-Controlled Byte Ordering in Double-Width Mode
After the first rising edge of the
rx_enabyteord
signal in
Figure 2–95
,
the byte ordering block finds the byte ordering pattern A in the second
most significant byte. It adds two pad bytes PD to push the byte ordering
pattern to the least significant byte position and asserts the
rx_byteorderalignstatus
signal. After the second rising edge of the
rx_enabyteord
signal,
rx_byteorderalignstatus
is de-asserted
and the byte ordering block starts looking for byte ordering pattern A. It
finds the byte ordering pattern A in the second least significant byte
position and adds three pad bytes PD. The byte ordering pattern A now
appears at the least significant byte position and
rx_byteordalignstatus
is asserted.
D1
A
X
X
D5
D4
D3
D2
D2
D1
A
X
D6
D5
D4
D3
rx_enabyteord
PD
PD
X
X
D3
D2
D1
A
PD
PD
PD
X
D3
D2
D1
A
rx_byteordalignstatus
Input to Byte Ordering Block
Output from Byte Ordering Block