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AD7779 SYNCout dont work in SPI mode

Question asked by www_cool on Oct 26, 2016
Latest reply on Oct 28, 2016 by musach

Hi, i tryed to set four AD7779 in daisy chain mode. So i need sync all ADs to get sync RDY signals on them and sync data sample start time on all ADs. 

We set  FORMAT0 = 1 and  FORMAT1 = 1 to use SPI mode.

All registers read and write fine by SPI Master, so we config dec rate, DCLK divider and MCLK divider as we need and get fine results, but when we try to write SYNC  (AD7779_REG_GENERAL_USER_CONFIG_2 bit0) nothing happens on SYNCOUT line no matter 0 or 1 we write. START pin connected to GND. 

PIC.1 - START of controller - 4 RDY and SYNC (global line for all ADs). SYNC triggred only on start and after always in low level.