NOVATECH INSTRUMENTS
4
DDS9m Manual
Table 2: RS232 Serial Commands
RS232 Command
Function
Fn xxx.xxxxxxx
Set Frequency of output “n” in MHz to nearest 0.1Hz. Decimal point required.
n=0, 1, 2, 3. Maximum setting: 171.1276031MHz. Single tone mode.
Pn N
Set Phase of output “n.” N is an integer from 0 to 16383. Phase is set to N*360
o
/
16384 or N*
π
/8192 radians. Sets the relative phase of the frequency output
depending upon the value of n=0, 1, 2, 3. Single tone mode.
E x
Serial echo control. x=D for Echo Disable, x=E for Echo Enable
C x
Select clock source. x=E for External clock, x=I for Internal Clock. May require
adjustment of Kp and external filtering of output when an external clock is used.
R
Reset. This command resets the DDS9m. EEPROM data is preserved and, if valid,
is used upon restart. This is the same as cycling power.
CLR
Clear. This command clears the EEPROM valid flag and restores all factory
default values.
A x
CMOS output control. x=E for LVCMOS Enable, x=D for LVCMOS Disable.
S
Saves current state into EEPROM and sets valid flag. State used as default upon
next power up or reset. Use the
“CLR”
command to return to default values.
QUE
Return present frequency, phase and status. Returns a character string of all inter-
nal settings.
M N
Mode command. Mode ‘0’ is single tone on all channels (default). If N=a, then the
phase is automatically cleared during each command; if N=n, then the phase is not
cleared (default). See Section 4 for details.
Vn N
Set voltage level of output “n.” In default, the amplitude is set to the maximum:
approximately 1V
pp
(+4dBm) into 50
Ω.
N can range from 0 (off) to 1023 (no
decimal point allowed). Voltage level is scaled by N/1023. n=0, 1, 2, 3 to set the
amplitude on frequency 0, 1, 2 or 3. If N >=1024, the scaling is turned off and the
selected output is set to full scale.
Vs N
Set the output scaling factor. N=1 for full scale, N=2 for half scale, N=4 for one
quarter scale and N=8 for one eighth scale. All channels are scaled equally.
Kp aa
Set the DDS on-chip PLL reference multiplier constant. Must be one Hexadecimal
byte as two characters. Legal values are 1 (bypass PLL) and 4 to 20 (01
h
, 04
h
to
14
h
). Values of Kp times clock frequency must not be between 160MHz and
255MHz (for internal clock, this disallows 5<=Kp<= 9). (see paragraph 4.12 for
other considerations)
I x
Set the I/O update pulse method. If x=a, then an I/O update is issued automatically
at the end of each serial command (default). If x=m, then a manual I/O update
pulse is expected to be sent by a subsequent
‘I p’
command. See section 4.
B aa[bb[cc[dd[ee[ff[gg]]]]]]
This Byte command allows each register in the DDS chip to be set. Different
registers require a various number of bytes to be written depending upon the
function. Please consult the Analog Devices AD9959 data sheet for details. Note
that it is possible to set the DDS chip into a non-functional mode, requiring a
power cycle to recover. All values are in hexadecimal and no error checking, other
than correct format, is performed.
