AnsweredAssumed Answered

AD9859 Problem

Question asked by Yones on Apr 6, 2012
Latest reply on May 22, 2012 by DSB

Hi, i'm actually a French student in electronic,


I've been placed on a project which need a regulable sinusoïde, so i choose the AD9859 with a ADuC7026 to control it.

And whenever i send a reading request the DDS answer unexpected content.


For example i first try to fill the FTW so i send 8 BIT first to select the register : 0x04 and then i send 32BIT to fill it, and nearly 100µs after i send a reading request  : 0x84 and after I provide the clock so the DDS can answer me.

• Of course during all thoses operation i activate the /CS when i send and when i expect to recive.

I send the SPI request with MSB First, the serial clock is set at the beginning of each serial bit transfer and the clock is set @ 1.024MHz

so here is an oscillogramme.

the first 40 BIT are the filling of FTW and the second are the demand of reading FTW

The Yellow signal is the clock, the Blue is the MOSI, the purple the /CS and the green one is the MISO



and so here is my question, so far I've tried to read all registers and i had only stranges answers or nothing at all

Are some registers unreadable ?