AD9954/PCB Analog Devices Inc, AD9954/PCB Datasheet - Page 19

• Manufacturer Part Number: AD9954/PCB
• Description: BOARD EVAL FOR AD9954
• Manufacturer: Analog Devices Inc

Specifications of AD9954/PCB

• Rohs Status: RoHS non-compliant

Linear Sweep No-Dwell Feature
See CFR1<2> in the register maps (see Table 12 and Table 13)
for general details of the no-dwell mode. Figure 22 depicts the
linear sweep mode operation when the linear sweep no-dwell
bit is set. The Label A points indicate where a rising edge on
PS0 is detected; the Label B points indicate where the AD9954
has determined f
automatically returns to the starting frequency. Note that in this
mode, only sweeps from FTW0 to FTW1 using the positive
linear sweep control word are supported. Toggling PS0 from 1
to 0 neither initiates a falling sweep when the no-dwell bit is set,
nor interrupts a positive sweep already underway.
OUT
FTW1
FTW0
FTW1
FTW0
has reached the terminal frequency and
f
f
OUT
OUT
SINGLE-TONE
SINGLE-TONE
MODE
MODE
PS<0> = 0
PS<0> = 0
AT POINT A: LOAD RISING RAMP RATE REGISTER, APPLY RISING DFTW.
AT POINT B: LOAD FALLING RAMP RATE REGISTER, APPLY FALLING DFTW.
Figure 22. Linear Sweep Using No-Dwell Frequency Plan
A
A
PS<0> = 1 PS<0> = 0
Figure 21. Linear Sweep Frequency Plan
LINEAR SWEEP MODE ENABLE–NO DWELL BIT SET
LINEAR SWEEP MODE
PS<0> = 1
B
Rev. B | Page 19 of 40
A
PS<0> = 1
Resetting the Ramp Rate Timer
The ramp timer can be reset before reaching a count of 1 by
three methods.
Method one is by changing the PS0 input pin. When the PS0
input pin toggles from 0 to 1, the RSRRW value is loaded into
the ramp rate timer, which then proceeds to countdown as
normal. When the PS0 input pin toggles from 0 to 1, the falling
sweep ramp rate word (FSRRW) value is loaded into the ramp
rate timer, which then proceeds to countdown as normal.
The second method uses the LOAD SRR @ I/O UD bit
(CFR1<15>), see Table 12 for details.
B
B
PS<0> = 0
PS<0> = 0
A
PS<0> = 1
B
TIME
TIME
AD9954