Texas Instruments TMS320C6457 DSP manual Output Parameters Transfer

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3.Null EDMA3 transfer parameters (with all zeros), if there are no more user channels ready to be decoded and the OUTF bit is cleared.

9.2.1.5Output Parameters Transfer

This EDMA3 transfer is optional and depends on the OUTF bit in the TCP2 input configuration register 0 (TCPIC0). This EDMA3 transfer is a TCPREVT frame-synchronized transfer. The parameters should be set as:

∙OPTIONS:

–ITCCEN = 0 (Intermediate transfer complete chaining is disabled)

–TCCEN = 0 (Transfer complete chaining is disabled)

–ITCINTEN = 0 (Intermediate transfer complete interrupt is disabled)

–TCINTEN = 1 (Transfer complete interrupt is enabled)

–TCC = 1 to 63 (Transfer Complete Code)

–TCCMODE = 0 (Normal Completion)

–FWID = Don't care

–STAT = 0 (Entry is updated as normal)

–SYNCDIM = 0 (A-Sync. Each event triggers the transfer of ACNT elements.)

–DAM = 0 (Dst addressing within an array increments. Dst is not a FIFO)

–SAM = 0 (Src addressing within an array increments. Source is not a FIFO.)

∙SOURCE ADDRESS: TCPOUT (5000 0030h)

∙ACNT = 12 (No of bytes in an array)

∙BCNT = 1 (No of arrays of length ACNT)

∙DESTINATION ADDRESS: User output parameters start address (must be double-word aligned)

∙SRCBIDX = 0 (Source 2nd Dimension Index)

∙DSTBIDX = 0 (Destination 2nd Dimension Index)

∙SRCCIDX = 0 (Source 3rd Dimension Index)

∙DSTCIDX = 0 (Destination 3rd Dimension Index)

∙CCNT = 1 (No of frames in a block)

∙BCNTRLD: Don't care

∙LINK ADDRESS: See cases 1 and 2 below

Upon completion, this EDMA3 transfer is linked to one of the following:

1.The hard decisions EDMA3 transfer parameters of the next user-channel, if there is one ready to be decoded.

2.Null EDMA3 transfer parameters (with all zeros), if there are no more user-channels ready to be decoded.

9.2.2Input Configurations Parameters Programming

The frame length (FL bits in TCPIC0) should be set to the number of information bits (prior to turbo-encoding and not including the rate or the tail bits).

The number of sub-blocks (NSB bits in TCPIC2), the reliability length (R bits in TCPIC1), and the prolog size (P bits in TCPIC2) should be set as described in Section 8.3. It should be noted that a 1 must be subtracted from the calculated R value prior to writing to TCPIC1.

The maximum number of iterations (MAXIT bits in TCPIC2) should be selected as a function of the overall system performance. A value 0 sets the maximum number of iterations to its maximum (32).

The SNR threshold ratio (SNR bits in TCPIC2) should be selected as a function of the overall system performance. A value 0 disables the stopping criteria algorithm.

The EMAXSTR bit can be enabled or disabled in TCPIC3 (0 = max star disabled (enable Max Log-MAP) 1 = max star enabled (enable log MAP)).

SPRUGK1–March 2009 TMS320C6457 Turbo-Decoder Coprocessor 2 69

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