AD7858/AD7858L
Interface Mode 2 Configuration
that no valid data is written to any of the registers. When using
the software conversion start and transferring data during con-
version Note 1 must be obeyed.
Figure 35 shows the flowchart for configuring the part in Inter-
face Mode 2. In this case the read and write operations take
place simultaneously via the serial port. Writing all 0s ensures
START
POWER-ON, APPLY CLKIN SIGNAL,
WAIT FOR AUTOMATIC CALIBRATION
SERIAL
INTERFACE
MODE
?
2
INITIATE
CONVERSION YES
IN
SOFTWARE
?
NO
TRANSFER
DATA DURING
CONVERSION
?
YES
PULSE CONVST PIN
APPLY SYNC (IF REQUIRED), SCLK, WRITE
TO CONTROL REGISTER SETTING CHANNEL,
(SEE NOTE 1)
NO
WRITE TO CONTROL REGISTER
APPLY SYNC (IF REQUIRED), SCLK, WRITE
TO CONTROL REGISTER SETTING CHANNEL
TRANSFER
YES
SETTING CONVST BIT TO 1,
READ PREVIOUS RESULT ON
DOUT PIN (SEE NOTES 1&2)
DATA DURING
CONVERSION
?
WRITE TO CONTROL REGISTER SETTING
CONVST BIT TO 1, READ
WAIT APPROX 200ns AFTER
CONVST RISING EDGE
NO
CURRENT CONVERSION RESULT
ON DOUT PIN (SEE NOTE 2)
WAIT FOR BUSY SIGNAL TO GO LOW
OR
WAIT FOR BUSY BIT = 0
WAIT FOR BUSY SIGNAL TO GO LOW
APPLY SYNC (IF REQUIRED), SCLK, READ
PREVIOUS CONVERSION RESULT ON DOUT
PIN, AND WRITE CHANNEL SELECTION
OR
WAIT FOR BUSY BIT = 0
APPLY SYNC (IF REQUIRED), SCLK,
READ CURRENT CONVERSION RESULT
ON DOUT PIN, AND WRITE CHANNEL
SELECTION
NOTES
1WHEN USING THE SOFTWARE CONVERSION START AND TRANSFERRING DATA DURING CONVERSION THE USER MUST ENSURE THE CONTROL REGISTER
WRITE OPERATION EXTENDS BEYOND THE FALLING EDGE OF BUSY. THE FALLING EDGE OF BUSY RESETS THE CONVST BIT TO 0 AND ONLY AFTER THIS
TIME CAN IT BE REPROGRAMMED TO 1 TO START THE NEXT CONVERSION.
2TWO SEPARATE WRITES ARE REQUIRED TO SET A NEW CHANNEL ADDRESS AND INITIATE A CONVERSION ON THAT NEW CHANNEL IN SOFTWARE AS
THE ACQUISITION TIME (2 tCLKIN) MUST ELAPSE BEFORE THE CONVERSION BEGINS. IF BOTH COMMANDS ARE ISSUED IN THE ONE WRITE THE
RESULT OF THIS CONVERSION SHOULD BE DISCARDED AND THE NEXT CONVERSION ON THAT SAME CHANNEL WILL PROVIDE CORRECT RESULTS.
Figure 35. Flowchart for Setting Up, Reading, and Writing in Interface Mode 2
REV. B
–27–
ADI [ ADI ]
