DS604 Datasheet, PDF (10/12 Pages) –

3GPP2 Turbo Encoder v2.0
Figure Top x-ref 6
Clock
RFD_IN
CE
RDY
RSC1_TAIL
RSC2_TAIL
RSC1_SYSTEMATIC
D _{RSC2_SYSTEMATIC}
RSC1_PARITY0
i^RSC2_PARITY0
x1 x2
x3
x'1 x'2
x'3
z1 z2
z3
z'1
z'2
z'3
x4 x5 ... ... xn-1 xn xn+1 xn+2 xn+3 x'n+1 x'n+2 x'n+3
x'4 x'5 ...
...
x'n-1 x'n
x'n+1 x'n+2 x'n+3
z4 z5 ...
...
zn-1 zn zn+1 zn+2 zn+3
z'4 z'5 ...
...
z'n-1 z'n
z'n+1 z'n+2 z'n+3
s_{x1 ... xn are the uninterleaved input bits, delayed, for block size n}
x’1 ... x’n are the interleaved input bits
c_{z1 ... zn+3 are the RSC1 Parity1 output bits}
z’1 ... z’n+3 are the RSC2 Parity0 output bits
o _{Figure 6: Output Timing}
Throughput
n _{Throughput is the average number of bits per second, as measured at the input. As mentioned previ-}
ously, the maximum throughput is achieved when the block size is constant. For each block, there is an
t _{overhead of 6 cycles due to the time required for the tail bits, plus another 3 cycles due to internal}
i _{delays. Therefore, throughput is also maximized by using the largest available block size. As a percent-}
n _{age of clock speed, for any fixed block size, the throughput is given by:}
Input data throughput = (blocksize /(blocksize+9)) * 100%
u _Latency
e ^{The latency of the encoder is the number of clock cycles between a valid-FD being sampled and the}
assertion of the RDY at the start of the corresponding output block. As the encoder is double-buffered,
this latency depends upon the relative sizes of the current block and the preceding block, and partly on
d _{internal delays.}
For two consecutive input blocks, of sizes blocksize^i-1and blocksizeⁱ, respectively:
If the preceding block size, blocksize^i-1, is greater than the current block size, blocksizeⁱ, the latency is
IP _{determined by the time required to finish reading the preceding block. Therefore, the latency for the}
current block is given by:
Latency = blocksize^i-1 + 20
If the current block size, blocksizeⁱ, is greater than or equal to the preceding block size, blocksize^i-1, the
latency is determined by the time required to write the current block to memory. In this case, the latency
for the current block is:
Latency = blocksizeⁱ + 17
10
www.xilinx.com
DS604 April 2, 2007
Product Specification