For example, Figure 24 shows that just prior to the DRDY
signal going LOW, the internal Data Output Register (DOR)
is updated. This update involves the Offset Calibration
Register (OCR) and the Full-Scale Register (FSR). If the
OCR or FSR are being written, their final value may not be
correct, and the result placed into the DOR will certainly not
be valid. Problems can also arise if certain bits of the
Command Register are being changed.
initiated, the update is blocked. The old output data will
remain in the DOR and the new data will be lost. The old
data will remain valid until the read operation has com-
pleted. In general, multiple instructions may be issued, but
the last one in any conversion period should be complete
within 24 • XIN clock periods of the next DRDY LOW
time. In this usage, “complete” refers to the point where
DRDY rises in Figures 17 and 19 (in the Timing Section).
Consult Figures 25 and 26 for the flow of serial data
during any one conversion period.
Note that reading the Data Output Register is an excep-
tion. If the DOR is being read when the internal update is
Start
Reading
ADS1212/13
drives DRDY LOW
Start
Writing
ADS1212/13
drives DRDY LOW
CS
state
CS
state
HIGH
HIGH
LOW
LOW
Continuous
Read
Mode?
CS
state
Yes
HIGH
LOW
No
ADS1212/13
generates 8 serial clock
cycles and receives
Instruction Register
data via SDIO
ADS1212/13
generates 8
serial clock cycles
and receives
Instruction Register
data via SDIO
ADS1212/13
generates n
serial clock cycles
and receives
specified
Use
SDIO for
output?
Yes
register data
via SDIO
No
SDOUT becomes
SDIO input to
active from tri-state
output transition
ADS1212/13
drives DRDY HIGH
ADS1212/13 generates n
serial clock cycles
and transmits specified
register data via SDOUT
ADS1212/13 generates n
serial clock cycles
and transmits specified
register data via SDIO
End
SDOUT returns to
tri-state condition
SDIO transitions to
tri-state condition
ADS1212/13
drives DRDY HIGH
End
FIGURE 25. Flowchart for Writing and Reading Register Data, Master Mode.
27
®
ADS1212, 1213
BB [ BURR-BROWN CORPORATION ]
