ADS8353: CFR Register Data Read Back

Rok Kimovec

Part Number: ADS8353

Dear Sir/madam,

I have a discrepancy in first four bits returned by ADS8353 when performing the readback of CFR register. The bits R15 R14 R13 and R12 are always 0 (confirmed with an oscilloscope) when I issue the CUFF read back command and not 0011 as they should be according the Table 10 of the datasheet. All other bits returned by CFR readback are as I set them with CFR write command. Likewise when I read REFDAC_A and REFDAC_B, R15 R14 R13 and R12 are as specified in the datasheet Table 10. Also the conversion results I get seems to be in ordered. So ADC is working as expected except for the CFR readback.

My current CRF readback procedure is:

Cfr write:

Set the CFR by sending 1000 and CFR.b10 and CFR.b6 to 1 (all others 0) all in one frame with 48 CLKs.

Cfr read:

Send one empty frame (all zeros) with 48 CLKs. (Frame F in 8.5.3 Data read operation of the datasheet)

Send 0011 and rest 0 to read back CFR. (Frame F+1 in 8.5.3 Data read operation of the datasheet)

Send one empty frame (all zeros) with 48 CLKs to get the values stored in CFR. (Frame F+2 in 8.5.3 Data read operation of the datasheet)

The CLK speed for a serial communication is currently set to 195kHz. CS between frames is set high for aprox. 1us.

Is this a known error or am I doing something wrong? I tried my procedure with two different ADCs and both exhibit the same behavior.

Best regards,

Rok

over 5 years ago

0 Ryan Andrews over 5 years ago

TI__Guru 60476 points

Hello Rok,

Thank you for your post!

Your procedure sounds correct and it appears that the device is working as expected when reading the other registers. Let me check with the team and see if this issue has come up in the past.

Best regards,

0 Rok Kimovec over 5 years ago in reply to Ryan Andrews

Prodigy 50 points

Dear Ryan,

do you have any aditional info for me regarding the data register readback.

Best regards,
Rok

0 Ryan Andrews over 5 years ago in reply to Rok Kimovec

TI__Guru 60476 points

Hi Rok,

Sorry for the delay here, we had a couple folks on vacation this week. Someone on the design team is looking at this behavior on the test bench setup now as this is a normal functional check that they do during validation. I hope to hear back from them in the next day or so.

Best regards,

0 Ryan Andrews over 5 years ago in reply to Ryan Andrews

TI__Guru 60476 points

Hi Rok,

Our design team was able to test the CFR register readback on the test bench yesterday. The first four bits read back as '0011'. They tried this with 20 MHz and 10 MHz clock frequencies and both cases worked as expected.

This confirms that what you are observing is not expected behavior.

Regards,

0 Rok Kimovec over 5 years ago in reply to Ryan Andrews

Prodigy 50 points

Dear Ryan,

that's the behaviour I was expecting. I will try to figure out what's going on in my case.

Thanks for all the help.

Best regards,

Rok

Data converters

Data converters forum

ADS8353: CFR Register Data Read Back