AD9953/PCB Analog Devices Inc, AD9953/PCB Datasheet - Page 23

• Manufacturer Part Number: AD9953/PCB
• Description: BOARD EVAL FOR AD9953
• Manufacturer: Analog Devices Inc
• Series: AgileRF™r
• Type: DDS (Direct Digital Synthesis)r

Specifications of AD9953/PCB

• Rohs Status: RoHS non-compliant
• Contents: Evaluation Board
• For Use With/related Products: AD9953

OSK Ramp Rate Timer
The OSK ramp rate timer is a loadable down counter, which
generates the clock signal to the 14-bit counter that generates
the internal scale factor. The ramp rate timer is loaded with the
value of the ASFR every time the counter reaches 1 (decimal).
This load and countdown operation continues for as long as the
timer is enabled, unless the timer is forced to load before
reaching a count of 1.
If the load OSK timer bit (CFR1<26>) is set, the ramp rate
timer is loaded upon an I/O UPDATE or upon reaching a value
of 1. The ramp timer can be loaded before reaching
by three methods.
DDS CORE
AMPLITUDE SCALE
FACTOR REGISTER
COS(X)
(ASF)
0
1
Figure 20. On-Of
0
a cou
OSK ENAB
nt of 1
FA
CFR<25
OUT
OSK PIN
Rev. A | Page 23 of 32
INC/D
CTOR GENERATO
AUTO SCALE
f Shaped Key
LE
>
EC ENABLE
UP/DN
HOLD
TO D
SYN
C_CLK
AC
ing Block Diagram
T
W
lo
d
T
lo
(C
T
l
in
sh
b
oaded before reaching a count of 1 is when going from the
R
own as normal.
eing set.
he first method of loading is by changing the OSK input pin.
he second method in which the sweep ramp rate timer can be
he third method in which the sweep ramp rate timer can be
aded into the ramp rate timer, which then proceeds to count
aded before reaching a count of 1 is if the load OSK timer bit
active auto shaped on-off keying mode to the active auto
aped on-off keying mode; that is, when the sweep enable bit is
hen the OSK input pin changes state, the ASFR value is
FR1<26>) is set and an I/O UPDATE is issued.
AUTO DESK
CFR1<24>
ENABLE
RAMP RATE TIMER
LOAD OSK TIMER
CFR1<26>
AMPLITUDE RAMP
RATE REGISTER
LOAD
(ASF)
DATA
EN
CLOCK
AD9953