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I need some another informations . At the start-up, I need to make a cycling of power-down and power-up to make sure having a correct start-up of the ADC. Could you give me the best sequence of dialog between my driver and the ADC : exact words to write with the status of CONVST and the other bits, the timings, etc... to be really sure. For the moment, I write with a period of 30us. I write 1000 times the word "0000000001" and after the word "0011000011". It seems to work correctly but I want to be sure that my bug disappeared.
When the power is first applied, the AD7811 is in power down mode. To ensure the part is properly reset after the supply has been applied, you should first attempt a power up of the IC by writing ones to the PD0 and PD1 bits, then issue a software reset by writing zeros then ones again to the PD0 and PD1 bits. This causes a full internal reset of the part to occur. We recommend the following sequence of events to occur for the reset: Write 0x6040 to the control register (powers up the part) Wait 1.5uS (power up time) Write 0x0040 to the control register (powers down the part) Write 0x6040 to the control register (powers up the part again) Wait 1.5uS before initialising the 1st conversion (power up time). The timing for these writes to the control register is shown on page 15 of the datasheet. The period of 30us should be OK - the part can work down to a period of 50ns. You should not need to write to the control register 1000 times - just the once will do.