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AD7985 Datasheet(PDF) 20 Page - Analog Devices |
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AD7985 Datasheet(HTML) 20 Page - Analog Devices |
20 / 29 page Data Sheet AD7985 Rev. C | Page 19 of 28 CS MODE, 3-WIRE WITHOUT BUSY INDICATOR This mode is usually used when a single AD7985 is connected to an SPI-compatible digital host. The connection diagram is shown in Figure 26, and the corresponding timing is given in Figure 27. With SDI tied to VIO, a rising edge on CNV initiates a con- version, selects CS mode, and forces SDO to high impedance. When a conversion is initiated, it continues until completion, irrespective of the state of CNV. This can be useful, for example, to bring CNV low to select other SPI devices, such as analog multiplexers; however, CNV must be returned high before the minimum conversion time elapses and then held high for the maximum possible conversion time to avoid the generation of the busy signal indicator. When the conversion is complete, the AD7985 enters the acquisition phase and powers down. When CNV goes low, the MSB is output onto SDO. The remaining data bits are clocked by subsequent SCK falling edges. The data is valid on both SCK edges. Although the rising edge can capture the data, a digital host using the SCK falling edge allows a faster reading rate, provided that it has an acceptable hold time. After the 16th SCK falling edge or when CNV goes high (whichever occurs first), SDO returns to high impedance. AD7985 SDI SDO CNV SCK CONVERT DATA IN CLK DIGITAL HOST VIO Figure 26. CS Mode, 3-Wire Without Busy Indicator Connection Diagram (SDI High) ACQUISITION (n) ACQUISITION (n + 1) ACQUISITION (n – 1) 1 2 BEGIN DATA (n – 1) CONVERSION (n) END DATA (n – 1) SCK CNV SDO 14 15 CONVERSION (n – 1) END DATA (n – 2) tCONV tDATA 0 (I/O QUIET TIME) (I/O QUIET TIME) 16 14 15 16 1 15 14 13 2 0 1 2 SDI = 1 > tCONV (I/O QUIET TIME) tCYC tACQ tCNVH tQUIET tSCK tDIS tDIS tDIS tDIS tEN tEN tDSDO tHSDO tDATA tCONV Figure 27. CS Mode, 3-Wire Without Busy Indicator Serial Interface Timing (SDI High) |
Similar Part No. - AD7985_17 |
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Similar Description - AD7985_17 |
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