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VC33 to AD50C code

Started by Bill Finger January 27, 2004

Does anyone know of any example code to get the VC33 to talk to the AD50C,
as they're set up on the Spectrum Digital ezDSP? I think I'm most of the
way there, but somethings amiss...

Bill



Hi Bill

I am no expert on the TLC320AD50 (sorry no code), but in some ways it is
quite similar to the TLC32040 codec (C31 DSK), but in other ways very
different. What I see is a similar interface that has been augmented with
the ability to block accidental reprogrammation via an inadvertant DAC
value. The sticky point is probably codec 'secondary' programmations, or
that you have got stuck in a mode and cant get out.

How are 2nd XMIT's blocked or forced (how I interpret the DS)
-------------------------
In the 15b DAC mode the data words LSB bit is used to signal that a
secondary transmit is being requested. On the other hand, if modeb,
using the LSB would not be feasible since that bit is now effectively
random. Therefor in 16b mode a method of forcing 15b DAC mode or forcing
secondary transmits (FC pin) is needed.

If modeb
-----------
Program like a TLC32040, but be sure to write the 15/16b mode bit *LAST* as
this will block subsequent programmation attempts using LSB initiated transfers.

If modeb
-----------
LSB initiated secondaries are blocked in 16b mode and therefor require FC=1.
The timing is important since the rising edged of FSX latches the signal.
Just be sure that nothing else is going on that could delay the ISR.

Also, serial port data is clocked out from a *copy* of the DXR register
delaying the data stream. In the 15b mode the LSB is nominally used to
initiate programmation and this works since the stream is continuous.
However, in 16b mode the data stream must lead the FC=1 condition.

Hit Reset and Reprogram
-----------------------
Another option would be to simply pull the reset and reprogram the codec.
This might produce a pop, but it would get you back into a mode that can be
programmed.

As a recap, I see two potential snares

1) When the DAC is put into 16b mode, LSB initiated programmation is blocked
2) Using FC requires knowing that the serial port has a built-in delay

Hope this helps,
Keith Larson
----------------
At 07:51 AM 1/27/04 -0500, you wrote:

Does anyone know of any example code to get the VC33 to talk to the AD50C,
as they're set up on the Spectrum Digital ezDSP? I think I'm most of the
way there, but somethings amiss...

Bill

+--------------------------+
| Keith Larson |
| Member Group Technical Staff |
| Texas Instruments Incorporated |
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| 281-274-3288 |
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| www.micro.ti.com/~klarson (TI internal web only) |
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| TMS320C3x/C4x/VC33 Applications |
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| TMS320VC33 |
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