Power consumption on C5505 based design changing 20mA by adding 'no-op' instructions.

Hi,

The supply current will shift from 135mA@3.7 to 115mA@3.7 after the following code inside the function 'check_boot_record'.
ATA_readSector(boot_record_sector + l_reserved_sectors , pAtaDrive, pAtaDrive->_AtaWriteBuffer, 0);

But, the supply current will only shift to 115mA if the whole code including some 'nop' instructions.

Has anyone ever encountered this symptom before? Both CSL-3.3 and 2.5 have the same symptom under CCSv5.4.

Thanks.

Hi Jack,

Check the assembly output of the build to compare the differences in output.

Or set a breakpoint at this function and view the dissassembly from CCS. ASM single step into the function to compare each function call.

Hope this helps,
Mark 

Hi Mark,

Thanks for the suggestion. The symptom was caused by one uninitialized variable in the ATA buffer.

Jack

FYI:

There is another board may down shift current by ~65mA, if the variable in the ATA buffer is not initialized properly.

If there is any TI guy can explain this symptom,  I would like to know the reason behind this.

Thanks,

Jack

Hi Jack,

Which variable in the ATA buffer is triggering the change? Can you copy and paste code or variable watch window?

Regards,
Mark

Hi Mark,

In the sample code ccs_v4.0_examples\mmc_sd\CSL_MMCSD_SdCardFSExample\csl_mmcsd_atafs_example.c line 417

    /* Set the temp write buffer */
    pAtaFile->pDrive->_AtaWriteBuffer = AtaWrBuf;

These two lines have been properly moved to line 376 in the sample code ccs_v5.0_examples.

as

    /* Set the temp write buffer */
    gpstrAtaDrive->_AtaWriteBuffer = AtaWrBuf;

Thanks,

Jack

Hi Jack,

I see it now.

Make sure to use the latest CSL (3.03) - there is no more directory called CCS4 as the CSL is now supporting CCS5 only.

Get it here: http://www.ti.com/tool/sprc133

I confirmed that CSL3.03 is using gpstrAtaDrive->_AtaWriteBuffer = AtaWrBuf;

c55xx_csl_2.50:
    /* Set the temp write buffer */
    pAtaFile->pDrive->_AtaWriteBuffer = AtaWrBuf;

c55xx_csl_3.00:
    /* Set the temp write buffer */
    pAtaFile->pDrive->_AtaWriteBuffer = AtaWrBuf;

c55xx_csl_3.01:
    /* Set the temp write buffer */
    pAtaFile->pDrive->_AtaWriteBuffer = AtaWrBuf;

c55xx_csl_3.03:
    /* Set the temp write buffer */
    gpstrAtaDrive->_AtaWriteBuffer = AtaWrBuf;

Hope this helps,
Mark

Hi Mark,

Actually, if I put the following codes in program will show the ~60mA down shift on power consumption.

Uint16 *memory_pointer;

memory_pointer = (Uint16 *) 0x296C83;

*memory_pointer = 0x1220;        // ====> after this line, ~60mA down shift

I think you can explain this symptom.

Thanks,

Jack