Datasheet

Data Sheet AD9837
Rev. A | Page 17 of 28
DATA WRITE
(SEE FIGURE 24)
SELECT DATA
SOURCES
WAIT 7/8 MCLK
CYCLES
CHANGE PHASE?
CHANGE FREQUENCY?
CHANGE DAC OUTPUT
FROM SIN TO TRIANGLE?
CHANGE OUTPUT TO
A DIGITAL SIGNAL?
CHANGE PHASE
REGISTER?
CHANGE FREQUENCY
REGISTER?
CONTROL REGISTER
WRITE
(SEE TABLE 7)
INITIALIZATION
(SEE FIGURE 23)
NO
NO
NO
NO
YES
NO
YES
YES
NO
YES
YES
YES
YES
YES
09070-026
CHANGE
FSEL BIT?
CHANGE
PSEL BIT?
Figure 22. Flowchart for AD9837 Initialization and Operation
INITIALIZATION
APPLY RESET
(CONTROL REGISTER WRITE)
RESET = 1
WRITE TO FREQUENCY AND PHASE REGISTERS
FREQ0 REG =
f
OUT0
/f
MCLK
× 2
28
FREQ1 REG = f
OUT1
/f
MCLK
× 2
28
PHASE0 AND PHASE1 REG = (PHASESHIFT × 2
12
)/2π
(SEE FIGURE 24)
SET RESET = 0
SELECT FREQUENCY REGISTERS
SELECT PHASE REGISTERS
(CONTROL REGISTER WRITE)
RESET BIT = 0
FSEL = SELECTED FREQUENCY REGISTER
PSEL = SELECTED PHASE REGISTER
09070-027
Figure 23. Flowchart for Initialization