SPIRIT1 datasheet(52/94 Pages) STMICROELECTRONICS

52 / 94 page

Transmission and reception

SPIRIT1

52/94

Doc ID 022758 Rev 3

Although the maximum TX signal BW should not exceed 750 kHz, the bandwidth of the

channel select filter in the receiver may need some extra bandwidth to cope with tolerances

in transmit and receive frequencies which depend on the tolerances of the used crystals.

9.6

Data coding and integrity check process

9.6.1

FEC

The device provides hardware support for error correction and detection.

Error correction can be either enabled or disabled according to link reliability and power

consumption needs. Convolutional coding with a rate=½ and k=4 is applied on the payload

and CRC before transmission (poly [13,17]). On the receiver side, error correction is

performed using soft Viterbi decoding.

To further improve error correction performance, a data interleaver is used when

convolutional coding is enabled. Data interleaving/de-interleaving is performed using a 4x4-

bit matrix interleaver.

To fill the entire matrix, at least 2 bytes of data payload are required (16 cells). In the

interleaver matrix, the encoded data bits are written along the rows and the sequence to

send to the modulator is obtained by reading the matrix elements along the columns of the

matrix. Consequently, in the de-interleaver, the received data from the demodulator are

written into the matrix along the columns, and sent to the FEC decoder reading them from

M=6

592.9

300.4

149.9

75.0

37.5

18.7

9.3

4.7

2.3

1.2

M=7

541.6

271.8

135.8

67.8

33.9

17.0

8.5

4.2

2.1

1.1

M=8

499.8

249.5

124.6

62.3

31.1

15.6

7.8

3.9

1.9

1.0

Table 28.

CHFLT_M and CHFLT_E value for channel filter bandwidth (in kHz, for fclk = 24 MHz)

Table 29.

CHFLT_M and CHFLT_E value for channel filter bandwidth (in kHz, for fclk = 26 MHz)

E=0

E=1

E=2

E=3

E=4

E=5

E=6

E=7

E=8

E=9

M=0

800.1

450.9

224.7

112.3

56.1

28.0

14.0

7.0

3.5

1.8

M=1

795.1

425.9

212.4

106.2

53.0

26.5

13.3

6.6

3.3

1.7

M=2

768.4

403.2

201.1

100.5

50.2

25.1

12.6

6.3

3.1

1.6

M=3

736.8

380.8

190.0

95.0

47.4

23.7

11.9

5.9

3.0

1.5

M=4

705.1

362.1

180.7

90.3

45.1

22.6

11.3

5.6

2.8

1.4

M=5

670.9

341.7

170.6

85.3

42.6

21.3

10.6

5.3

2.7

1.3

M=6

642.3

325.4

162.4

81.2

40.6

20.3

10.1

5.1

2.5

1.3

M=7

586.7

294.5

147.1

73.5

36.7

18.4

9.2

4.6

2.3

1.2

M=8

541.4

270.3

135.0

67.5

33.7

16.9

8.4

4.2

2.1

1.1

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