I used ad7656 to ad convert
In the range of -5V or less, an incorrect value comes out.
When -300mv is input, the value of -6 v is output,
When -1 v is input, the value of -5 v is output.
The input data was both int type and float type.
vref is a 2.5v input, and all 6 channels are being used.
Where should I refer if there is an incorrect setting?