DAC output error

[ZPC.1]

I'm using STM32F405VGT6 to output sine wave by using its dac.After every output sample,which is triggerd by timer, dac's data holding register 'DAC_DHR12R2' is not holding the data and is reset to zero.So the output wave is something like sine wave mixed with tooth wave.I am thinking whether dac is damaged since it had run sevral times without error before .

[waclawek.jan]

If the holding register is zero, why would be output other than zero?

How exactly are you writing to the output register? If you use DMA, read out its registers and check/post, also read out the array in memory from which you perform the DMA.

Don't you use a 32-bit array and 16-bit transfers from it?

JW