Reconfigurable cyclic shifter arrangement
In one embodiment, a reconfigurable cyclic shifter arrangement has first and second reconfigurable cyclic shifters connected in series that are each selectively and independently configurable to operate in any one of three different modes at a time. In a first mode, the reconfigurable cyclic shifter is configured as four 4×4 cyclic shifters to cyclically shift four sets of four input values. In a second mode, the reconfigurable cyclic shifter is configured as two 8×8 cyclic shifters to cyclically shift two sets of eight input values. In a third mode, the reconfigurable cyclic shifter is configured as one 16×16 cyclic shifter to cyclically shift one set of 16 input values. Because the first and second reconfigurable cyclic shifters are independently configurable, there are nine different configurations of the reconfigurable cyclic shifter arrangement.
1. An apparatus comprising a reconfigurable cyclic shifter arrangement, the reconfigurable cyclic shifter arrangement comprising:
a first reconfigurable cyclic shifter adapted to cyclically shift N input values, N≧4, to generate a first set of N output values;
a second reconfigurable cyclic shifter adapted to cyclically shift the first set of N output values to generate a second set of N output values; and
a controller adapted to selectively configure (i) the first reconfigurable cyclic shifter to operate in any one of at least first and second operating modes and (ii) the second reconfigurable cyclic shifter to operate in any one of the at least first and second operating modes, independent of the configuration of the first reconfigurable cyclic shifter, wherein:
a reconfigurable cyclic shifter configured in the first operating mode operates as a first set of cyclic shifters, the first set comprising one or more independent cyclic shifters, to independently cyclically shift one or more different subsets of N values; and
a reconfigurable cyclic shifter configured in the second operating mode operates as a second set of cyclic shifters, the second set comprising two or more independent cyclic shifters, to independently cyclically shift two or more different subsets of N values, wherein the number of independent cyclic shifters in the second set is greater than the number of independent cyclic shifters in the first set.
2. The apparatus of claim 1 , wherein:
in a first configuration of the reconfigurable cyclic shifter arrangement, the first and second reconfigurable cyclic shifters are both configured to operate in the first operating mode;
in a second configuration of the reconfigurable cyclic shifter arrangement, the first and second reconfigurable cyclic shifters are both configured to operate in the second operating mode;
in a third configuration of the reconfigurable cyclic shifter arrangement, the first reconfigurable cyclic shifter is configured to operate in the first mode and the second reconfigurable cyclic shifter is configured to operate in the second mode; and
in a fourth configuration of the reconfigurable cyclic shifter arrangement, the first reconfigurable cyclic shifter is configured to operate in the second mode and the second reconfigurable cyclic shifter is configured to operate in the first mode.
3. The apparatus of claim 2 , wherein the reconfigurable cyclic shifter arrangement is configured in either the third configuration or the fourth configuration.
4. The apparatus of claim 1 , further comprising:
a first multiplexer adapted to selectively output one of the first and second sets of N output values to a first data path; and
a second multiplexer adapted to selectively output a remaining one of the first and second sets of N output values to a second data path, different from the first data path.
5. The apparatus of claim 1 , wherein each of the first and second reconfigurable cyclic shifters comprises:
at least one pre-multiplexer stage comprising a plurality of multiplexers; and
at least two independent cyclic shifters, wherein:
the at least one pre-multiplexer stage is adapted to (i) receive N values and (ii) selectively output a different subset of the N values to each of the at least two independent cyclic shifters; and
each of the at least two independent cyclic shifters is adapted to independently cyclically shift the corresponding different subset of the N values.
6. The apparatus of claim 5 , wherein each of the multiplexers is a (2×1) multiplexer.
7. The apparatus of claim 5 , wherein each of the first and second reconfigurable cyclic shifters comprises a plurality of pre-multiplexer stages.
8. The apparatus of claim 1 , wherein the apparatus comprises a low-density parity-check (LDPC) decoder comprising the reconfigurable cyclic shifter arrangement.
9. The apparatus of claim 8 , wherein the LDPC decoder is adapted to decode codewords encoded based on an H-matrix having two or more different circulant sizes.
10. The apparatus of claim 1 , wherein:
the first set of N output values is shifted relative to the N input values; and
the second set of N output values is unshifted relative to the N input values.
11. The apparatus of claim 1 , wherein the apparatus is an integrated circuit.
12. An apparatus comprising a reconfigurable cyclic shifter arrangement, the reconfigurable cyclic shifter arrangement comprising:
first shifting means for cyclically shifting N input values, N>≧4, to generate a first set of N output values;
second shifting means for cyclically shifting the first set of N output values to generate a second set of N output values; and
control means for selectively configuring (i) the first means to operate in any one of at least first and second operating modes and (ii) the second means to operate in any one of the at least first and second operating modes, independent of the configuration of the first means, wherein:
in the first operating mode, the shifting means operates as a first set of cyclic shifters, the first set comprising one or more independent cyclic shifters, to independently cyclically shift one or more different subsets of N values; and
in the second operating mode, the shifting means operates as a second set of cyclic shifters, the second set comprising two or more independent cyclic shifters, to independently cyclically shift two or more different subsets of N values, wherein the number of independent cyclic shifters in the second set is greater than the number of independent cyclic shifters in the first set.
13. A machine-implemented method, the method comprising:
cyclically shifting N input values, N≧4, using a first reconfigurable cyclic shifter to generate a first set of N output values;
cyclically shifting the first set of N output values using a second reconfigurable cyclic shifter to generate a second set of N output values; and
selectively configuring (i) the first reconfigurable cyclic shifter to operate in any one of at least first and second operating modes and (ii) the second reconfigurable cyclic shifter to operate in any one of the at least first and second operating modes, independent of the configuration of the first reconfigurable cyclic shifter, wherein:
a reconfigurable cyclic shifter configured in the first operating mode operates as a first set of cyclic shifters, the first set comprising one or more independent cyclic shifters, to independently cyclically shift one or more different subsets of N values; and
a reconfigurable cyclic shifter configured in the second operating mode operates as a second set of cyclic shifters, the second set comprising two or more independent cyclic shifters, to independently cyclically shift two or more different subsets of N values, wherein the number of independent cyclic shifters in the second set is greater than the number of independent cyclic shifters in the first set.
14. The method of claim 13 , wherein:
in a first configuration, the first and second reconfigurable cyclic shifters are both configured to operate in the first operating mode;
in a second configuration, the first and second reconfigurable cyclic shifters are both configured to operate in the second operating mode;
in a third configuration, the first reconfigurable cyclic shifter is configured to operate in the first mode and the second reconfigurable cyclic shifter is configured to operate in the second mode; and
in a fourth configuration, the first reconfigurable cyclic shifter is configured to operate in the second mode and the second reconfigurable cyclic shifter is configured to operate in the first mode.
15. The method of claim 14 , wherein the reconfigurable cyclic shifter arrangement is configured in either the third configuration or the fourth configuration.
16. The method of claim 13 , further comprising:
selectively outputting one of the first and second sets of N output values to a first data path; and
selectively outputting a remaining one of the first and second sets of N output values to a second data path, different from the first data path.
17. The method of claim 13 , wherein each of the first and second reconfigurable cyclic shifters comprises:
at least one pre-multiplexer stage comprising a plurality of multiplexers; and
at least two independent cyclic shifters, wherein:
the at least one pre-multiplexer stage is adapted to (i) receive N values and (ii) selectively output a different subset of the N values to each of the at least two independent cyclic shifters; and
each of the at least two independent cyclic shifters is adapted to independently cyclically shift the corresponding different subset of the N values.
18. The method of claim 13 , wherein the method comprises performing low-density parity-check (LDPC) decoding of a codeword, wherein the cyclic shifting is a step performed in the LDPC decoding.
19. The method of claim 18 , wherein the LDPC decoding comprises decoding codewords encoded based on an H-matrix having two or more different circulant sizes.
20. The method of claim 13 , comprising:
shifting the first set of N output values relative to the N input values; and
shifting the second set of N output values relative to the N input values.