Marine Radio - Marine Radio Decoder User Manual

9.3.1.4 Extrinsics Transfer
9.3.2 Input Configurations Parameters Programming
www.ti.com Programming
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.
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.
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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