Multiple input channels, Multiple input channels -4 – Altera Reed-Solomon II MegaCore Function User Manual

Page 20

The codeword starts when you assert the

in_valid

signal and the

in_startofpacket

signal.The decoder

accepts the data at

in_data

as valid data. The codeword ends when you assert the

in_endofpacket

signal.

For a 1-channel codeword, assert the

in_startofpacket

and

in_endofpacket

signals for one clock cycle.

When the decoder deasserts the

in_ready

signal, the decoder cannot process any more data until it

asserts the

in_ready

signal again.

At the output, the operation is identical. When the decoder asserts the

out_valid

signal and the

out_startofpacket

signal, the decoder provides valid data on

out_data

. The decoder asserts the

out_startofpacket

signal and the

out_endofpacket

signal to indicate the start and end of a codeword.

The decoder automatically detects and corrects errors in a codeword and asserts the

out_error

signal

when it encounters a non-correctable codeword. The decoder outputs the full codeword including the

check symbols, which you should remove.

Variable Decoding

Under normal circumstances, the decoder allow variable decoding—you can change the number of

symbols per codeword (N) using

sink_eop

, but not the number of check symbols while decoding.

However, you cannot change the length of the codeword, if you turn on the erasure-supporting option. If

you turn on the variable option, you can vary the number of symbols per codeword (using the

numn

signal) and the number of check symbols (using the

numcheck

signal), in real time, from their minimum

allowable values up to their selected values, even with the erasures-supporting option turned on.

Multiple Input Channels

The RS II IP core processes multiple input channels simultaneously.
The IP core receives codewords in a fixed pattern. Symbols coming in through the channels are

interleaved. The IP core samples the first symbol of channel one on the first rising clock edge, then the

first symbol of channel two on the second rising clock edge, etc. Both information and check symbols are

output in the same sequence.

Figure 3-5: Codeword for

Channels and

Symbols

The channel signal indicates the channel associated to the current symbol. The channel sequence is fixed.

startofpacket

indicates the first symbol of a codeword per channel. For a C-channel codeword,

startofpacket

must be high for C consecutive cycles.

endofpacket

indicates the last symbol of a

codeword per channel. For a C-channel codeword,

endofpacket

must be high for C consecutive cycles.

valid

startofpacket

endofpacket

channel

data

Codeword 1

Codeword 0

ch 1. N-1

ch 0. N-1

ch 1.1

ch 0.1

ch 1.0

ch 0.0

...

...
...

ch 1. N-1 ch 1. N-1

ch 0. N-1 ch 1. N-1

Note: The

startofpacket

and

endofpacket

governs the number of symbols per codeword, N. The IP

core does not verify if N exceeds the maximum symbols per codeword. The IP core also does not

verify the channel or data pattern. You must ensure that the codeword sent to the IP core has a

valid N and a valid pattern.

3-4

Multiple Input Channels

UG-01090

2015.05.01

Altera Corporation

Reed-Solomon II IP Core Functional Description

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