Introduction
The DPA data-realignment circuitry allows further realignment beyond
what the J multiplication factor allows. You can set the J multiplication
factor to be 8 or 10. However, because data must be continuously clocked
in on each low-speed clock cycle, the upcoming bit to be realigned and
previous n −1 bits of data are selected each time the data realignment
logic’s counter passes n −1. At this point the data is selected entirely from
bit-slip register 3 (see Figure 3–11) as the counter is reset to 0. The logic
array receives a new valid byte of data on the next divided low speed
clock cycle. Figure 3–11 shows the data realignment logic output
selection from data in the data realignment register 2 and data
realignment register 3 based on its current counter value upon
continuous request of data slipping from the logic array.
Figure 3–11. DPA Data Realigner
Bit Slip
Register 2 Register 3
Bit Slip
Bit Slip
Register 2 Register 3
Bit Slip
Bit Slip
Register 2 Register 3
Bit Slip
Bit Slip
Register 2 Register 3
Bit Slip
Bit Slip
Register 2 Register 3
Bit Slip
D19
D18
D17
D16
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
D29
D28
D27
D26
D25
D24
D23
D22
D21
D20
D19
D18
D17
D16
D15
D14
D13
D12
D11
D10
D99
D98
D97
D96
D95
D94
D93
D92
D91
D90
D89
D18
D87
D86
D85
D84
D83
D82
D81
D80
D119
D118
D117
D116
D115
D114
D113
D112
D111
D110
D99
D98
D97
D96
D95
D94
D93
D92
D91
D90
D119
D118
D117
D116
D115
D114
D113
D112
D111
D110
D109
D108
D107
D106
D125
D124
D123
D102
D101
D100
One bit
slipped
Seven more
bits slipped
One more
bit slipped
One more
bit slipped
Zero bits slipped.
Counter = 0
D10 is the upcoming
bit to be slipped.
One bit slipped.
Counter = 1
D21 is the upcoming
bit to be slipped.
Eight bits slipped.
Counter = 8
D98 is the upcoming
bit to be slipped.
Nine bits slipped.
Counter = 9
D119 is the upcoming
bit to be slipped.
10 bits slipped.
Counter = 0
Real data will resume
on the next byte.
Use the rx_channel_data_alignsignal within the device to activate
the data realigner. You can use internal logic or an external pin to control
the rx_channel_data_alignsignal. To ensure the rising edge of the
rx_channel_data_alignsignal is latched into the control logic, the
rx_channel_data_alignsignal should stay high for at least two low-
frequency clock cycles.
3–14
Stratix GX Device Handbook, Volume 1
Altera Corporation
August 2005
ALTERA [ ALTERA CORPORATION ]
