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LTC2666-16 MISO output

Question asked by kahlenberg on Jul 30, 2018
Latest reply on Aug 1, 2018 by kahlenberg

Hi,

I designed a hardware with LTC2666 16bit DAC and I want to output some signals by giving the correct commands (I hope). However, When I send command, address and data word, MISO (or SDO) word doesn't match with the previous input (MOSI or SDI) word. It must give previous 32 bit data-word. Therefore analog outputs don't change. I also have a problem with signal level on MISO. I attach the picture at the end.

These are pictures from osciloscope to show all signals.

 

Green  (CH4): MOSI (SDI)

Magenta (CH3): MISO (SDO)

Turkis (CH2): SCK

Orange (CH1): nCS

 

This is command 0x00A0<some random number>, write code to all, update code all

 

 

Current MISO data doesn't match with previous one:

 

 

One more strange thing is that the first 16-bit of MISO is always zero.

 

 

There is a digital isolator (ISO7763 from TI)  between µC and DAC, and MISO signal goes very slowly to 3.3V level after CS signal is released (goes to 1). There is no push-down or pull-up resistors on lines.

 

 

Thanks in advance.

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