Texas Instruments TMS320C6457 DSP manual Extrinsics Transfer

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

2.Dummy EDMA3 transfer parameters, if there are no more user channels LOG-MAP ready to be decoded.

9.3.1.4Extrinsics Transfer

This EDMA3 transfer to the extrinsics buffer 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 disabled)

–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.)

∙If the OPMODE == FIRST_SUB_FRAME SOURCE ADDRESS: TCPEXT (5003 0000h)

∙If the OPMODE == MIDDLE_SUB_FRAME or LAST_SUB_FRAME SOURCE ADDRESS: TCPEXT (5003 0000h + prolog_length)

∙ACNT = 8 * ceil ((frame_length)/8) ⇒ (No of bytes in an array)

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

∙DESTINATION ADDRESS: User extrinsics 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 EDMA3 extrinsics transfer parameters of the next user-channel, if there is one ready to be decoded.

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

9.3.2Input Configurations Parameters Programming

The frame length (FL bits in TCPIC0) should be set to the total shared-processing frame length (prior to turbo-encoding and not including any tail information).

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

∙The SNR threshold ratio (SNR bits in TCPIC2) should be disabled.

∙The CRC bits in (TCPIC4) should be disabled.

∙The prolog reduction should be disabled.

∙The extrinsic scaling should be disabled.

SPRUGK1–March 2009 TMS320C6457 Turbo-Decoder Coprocessor 2 73

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