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Integer-Output RS Decoder HDL Optimized

Decode data using a Reed-Solomon decoder


Block sublibrary of Error Correction and Detection


Reed-Solomon encoding follows the same standards as any other cyclic redundancy code. The Integer-Output RS Decoder HDL Optimized block can be used to model many communication system Forward Error Correcting (FEC) codes.

For more about the Reed-Solomon decoder, see the Integer-Output RS Decoder block reference. For more information on representing data for Reed-Solomon codes, see Integer Format (Reed-Solomon Only).

Signal Attributes

The Integer-Output RS Decoder HDL Optimized block has four input ports and six output ports (5 required, 1 optional).

PortDirectionDescriptionData Type
dataInInputMessage data, one symbol at a time.Integer or fixdt with any binary point scaling. double is allowed for simulation but not for HDL code generation.
startInInputIndicates the start of a frame of data. Boolean
endInInputIndicates the end of a frame of data. Boolean
validInInputIndicates that input data is valid. Boolean
dataOutOutputMessage data with the checksum appended. The data width is the same as the input data port. Same as dataIn
startOutOutputIndicates the start of a frame of data. Boolean
endOutOutputIndicates the end of a frame of data, including checksum. Boolean
validOutOutputIndicates that output data is valid. Boolean
errOutOutputIndicates the corruption of the received data when error is high.Boolean
numErrorsOutput (optional)Count of detected errors.uint8


  • Each input frame must contain more than (N-K)*2 symbols, and fewer than or equal to N symbols. A shortened code is inferred when the number of valid data samples between startIn and endIn is less than N. A shortened code still requires N cycles to perform the Chien search. If the input is less than N symbols, leave a guard interval of at least N-size inactive cycles before starting the next frame.

  • The decoder can operate on up to 4 messages at a time. If the block receives the start of a fifth message before completely decoding the first message, the block drops data samples from the first message. To avoid this issue, increase the number of inactive cycles between input messages.

  • The generator polynomial is not specified explicitly. However, it is defined by the code word length, the message length, and the B value for the starting exponent of the roots. To get the value of B from a generator polynomial, use the genpoly2b function.


Codeword length

The length of the code word in symbols, N, must be equal to 2M-1, where M is the input word length. M can be between 3 and 16 bits.

Message length

The message length in symbols, K. The number of parity symbols, N-K, must be a positive even integer, greater than or equal to the input word length, M.

Source of primitive polynomial

Select Property to enable the Primitive polynomial parameter.

Primitive polynomial

Binary row vector representing the primitive polynomial in descending order of powers. When you provide a primitive polynomial, the number of input bits must be an integer multiple of K times the order of the primitive polynomial instead.

This parameter applies when only when Property is selected for Primitive polynomial.

Source of B, the starting power for roots of the primitive polynomial

Select Property to enable the B value parameter. When you select Auto, the block uses B = 1.

B value

The starting exponent of the roots.

This field is available only when you select Property for Source of B, the starting power for roots of the primitive polynomial. The default is 1.

Enable number of errors output

Check this box to enable the numErrors output port. This port outputs the detected symbol error count.


Timing Diagram

Extended Capabilities

Introduced in R2012b