DS634 Datasheet, PDF (7/20 Pages) –

IEEE 802.16e CTC Decoder v4.0
Figure 6 shows a timing diagram for the decoder inputs. Ncode, NumIter, earlyterm, and ex_scale must
be valid by the time start_in pulses High. The start_in signal pulses High for one clock and must occur
with the first data_en of each input code block. The data_en signal is High for each data_in (data_in
represents Adata_in, Bdata_in, Y1data_in, Y2data_in, W1data_in, W2data_in, EX1data_in, and
EX2data_in) sample to be processed. Although the timing diagram shows data_en High continuously
for a block of time, the decoder also supports an arbitrary data_en pattern.
The Ncode, NumIter, earlyterm and ex_scale signals can change from one block to the next without
interruption of the data flow. These signals are latched into the decoder by the start_in pulse and other
internal strobes. This allows the Ncode, NumIter, earlyterm, and ex_scale parameters to follow the
Dinput code block as it is being processed by various stages of the decoder.
X-Ref Target - Figure 6
X-Ref Target - Figure 6
clk
is_{data_in}
D₀
D₁
D₂ D₃
D₄
D₅ D₆
D₇
D₈
D₉ D₁₀
D₁₁ D₁₂
c_{data_en}
o _{start_in}
n _Ncode
24, 36, 48, 72, 96, 108, 120, 144, 180, 192, 216, or 240
ti _Numlter
1 to 255
n _{Figure 6: Timing Diagram for CTC Decoder Inputs}
ds634_06_05/21/07
u _{Figure 7 shows a timing diagram for the decoder outputs. The start_out signal pulses High with the}
first output bit of each decoded block. The dataout_valid signal is High for as long as data_out
e _{(data_out represents Adata_out, Bdata_out, EX1data_out, and EX2data_out) contains valid data. The}
dataout_valid signal can be used as a data enable for downstream processing of data_out. The
d dataout_valid signal bursts High for a duration of N clks. If necessary, the decoder output can be com-
bined with an external FIFO for further data flow control.
X-Ref Target - Figure 7
X-Ref Target - Figure 7
IP _clk
data_out
D₀
D₁
D₂ D₃
D₄
D₅ D₆
D₇
D₈
D₉ D₁₀
D₁₁ D₁₂
dataout_valid
start_out
Figure 7: Timing Diagram for CTC Decoder Outputs
ds634_07_052107
DS634 December 2, 2009
www.xilinx.com
7
Product Specification