ADS7890

SLAS409 − DECEMBER 2003

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11

2

3

9

2

3

15

16

D12

MSB-D13

MSB-D13

LSB-D0

Data From Last Conversion

SCLK

FS

CS

BUSY

SDO

Figure 9. Frame Abort Using CS Before Sample Start

The rising edge of FS (see Figure 10) or rising edge of CS (see Figure 11) during a sample period (td8 after the

9th rising edge of SCLK) to the 16th falling edge of SCLK aborts the sample and the device enters the

conversion phase, this also aborts the current data out operation on SDO (if aborted before 14th clock). As

expected, SDO goes to three-state with CS high. The conversion results can be latched in the next frame,

however reliability of the data depends on the sampling time available before the frame abort.

MSB− D13

D12

LSB−D0

td8

2

3

9

10

16

SCLK

FS

BUSY

CS

SDO

(Held Low)

Figure 10. Frame Abort Using FS During Sample

MSB− D13

D12

2

3

9

10

16

td8

SCLK

FS

BUSY

CS

SDO

Figure 11. Frame Abort Using CS During Sample

The rising edge of FS during a conversion (from BUSY high until the end of t(conv) as shown in Figure 12) aborts

the ongoing conversion. This starts the next frame. The device outputs 3F80 (hex) on SDO during the first frame

after the conversion abort. Toggling CS during a conversion (with FS low) does not have any effect on the

conversion.