VCP2 frame and sliding window length errors

Michael Miller3

Hi. I'm encountering VCP2 errors in the VCP2 error register of FCTLERR and FTLERR for sizes that i thought are well below the published limits. (I do get the VCP2 to function correctly for even smaller sizes). So here are a few setups:

WiMAX Settings taken from VCP2_TailBiting_WiMax_ConvCodec_tci6482 example:

oVcpCurrentParams.frameLen = 288 + 2 * 18;
oVcpCurrentParams.rate = VCP2_RATE_1_2;
oVcpCurrentParams.constLen = 7;
oVcpCurrentParams.yamTh = 0;
oVcpCurrentParams.stateNum = 0x400;
oVcpCurrentParams.decision = VCP2_DECISION_HARD;
oVcpCurrentParams.readFlag = 1;
oVcpCurrentParams.tbConvrgMode = 1;
oVcpCurrentParams.tailBitEnable = 0;
oVcpCurrentParams.traceBackIndex = 0;
oVcpCurrentParams.outOrder = 1;
oVcpCurrentParams.perf = VCP2_SPEED_MOST_CRITICAL;

gives Config registers of:

g_oVcpConfigIc
0035391B 00000000 01440144 10000012 00000400 605F0000

and configuration bus registers of:
0x021D0000 480A0000 00000000 00000000 00000000 00000000 00000000 00000001 00000000
0x021D0020 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
0x021D0040 0000001A 00000000 00000000 00000000 00000029 00000000 00000000 00000000
0x021D0060 00000001

I also get an error for a much simpler shorter length case (non-convergent mode with tail bits)
oVcpCurrentParams.frameLen = 140;
oVcpCurrentParams.rate = VCP2_RATE_1_3;
oVcpCurrentParams.constLen = 7;
oVcpCurrentParams.yamTh = 0;
oVcpCurrentParams.stateNum = 0;
oVcpCurrentParams.decision = VCP2_DECISION_HARD;
oVcpCurrentParams.readFlag = 0;
oVcpCurrentParams.tbConvrgMode = 0;
oVcpCurrentParams.tailBitEnable = 1;
oVcpCurrentParams.traceBackIndex = 0;
oVcpCurrentParams.outOrder = VCP2_OUTORDER_31_0;
oVcpCurrentParams.perf = VCP2_SPEED_CRITICAL;

g_oVcpConfigIc
0035391B 00000000 0000008C 11000000 00000400 10270000

0x021D0000 480A0000 00000000 00000000 00000000 00000000 00000000 00000001 00000000
0x021D0020 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
0x021D0040 0000001A 00000000 00000000 00000000 00000005 00000000 00000000 00000000
0x021D0060 00000001

My expected values for constraint length of 7 for Fmax and (r+c)max were 378 symbols. Why am I hitting the limit for these cases? I’m targeting a C6670 chip, and have tried this on the simulator, eval board & target hardware with the same results. Your help is appreciated. Thanks.

over 11 years ago

0 Raja over 11 years ago

TI__Guru* 81335 points

Hi,

Apologize for the earlier post. We will support you shortly.

Thank you for your patience.

0 Nitin Sakhuja over 11 years ago in reply to Raja

TI__Mastermind 30405 points

Hi Michael,

I am looking into your query and will get back to you with a response. Can you please provide your VCP2 example project which I can build in CCS to help me look into it? Thanks

Regards

-Nitin

0 Michael Miller3 over 11 years ago in reply to Nitin Sakhuja

Prodigy 50 points

The WiMax settings were taken from the project in the following thread:

http://e2e.ti.com/support/dsp/tms320c6000_high_performance_dsps/f/112/t/69928.aspx?pi24527=1

0 Nitin Sakhuja over 11 years ago in reply to Michael Miller3

TI__Mastermind 30405 points

Hi Michael,

I need your ported version of this project which you created for C6670. Thanks.

Regards

-Nitin

0 Michael Miller3 over 11 years ago in reply to Nitin Sakhuja

Prodigy 50 points

Nitin,

Can you tell from the register values in the issue description if this is expected behavior or not for the VCP2? Thanks.

-Mike

0 Nitin Sakhuja over 11 years ago in reply to Michael Miller3

TI__Mastermind 30405 points

Hi Michael,

The r+c value is within the limit specified for HD mode with constraint length 7 and it should not produce FCTLERR. However there seems to be a problem in your input configuration. The first configuration specifies a code rate of 1/2 (oVcpCurrentParams.rate = VCP2_RATE_1_2) but the value in VCPIC0 specifies non-zero POLY0, POLY1 and POLY3 fields (0x0035391B).

As per the note given under Table3-4: The VCP2 uses the number of poly fields set to zero starting at POLY3 to determine the code rate. Therefore, POLYn fields not used by the current code rate must be set to zero. The VCP2 uses the number of least-significant bits that are zero in POLY0 to determine the constraint length.

The corresponding value of VCPIC0 in the example is 0x00006CE4 which complies with this requirement. This error effectively configures the VCP for code rate 1/3 and also creates a mismatch in the SYMX value in VCPIC5 which in the example is configured for code rate 1/2. The VCP error register in your output has bit-5 set which indicates this.

I would request you to fix the above error and also run the provided example on your platform to have a working reference. Thanks.

Regards

-Nitin

0 Michael Miller3 over 11 years ago in reply to Nitin Sakhuja

Prodigy 50 points

Sorry to have overlooked the settings of the generator polynomials for that example. On updating those, the VCP does run. Did you notice any issues with my 2nd example? That one still does not run. Thanks.

0 Michael Miller3 over 11 years ago in reply to Michael Miller3

Prodigy 50 points

My 2nd example also had a generator polynomial mistake. Thanks for pointing out that an invalid generator polynomial can cause these errors.

The config register for that example should have been:

g_oVcpConfigIc
00D4E46C 00000000 0000008C 11000000 00000400 10270000

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VCP2 frame and sliding window length errors