HP E1340A, User Manual

Page: 244 / 295

Setting the Signal
Frequency
There are five frequency parameters used with the AFG:
•
fixed (continuous) frequency
•
sweep start frequency
•
sweep stop frequency
•
FSK frequency 1
•
FSK frequency 2
Frequency Register 1 (command opcode 1) is used to set a fixed frequency,
the sweep start frequency, and the first FSK frequency. Frequency Register
2 (command opcode 2) is used to set a fixed frequency, the sweep stop
frequency, and the second FSK frequency.
Format
The frequency is a four-byte parameter expressed in 10’s of millihertz. The
format of the frequency value set from the Parameter Register is as follows:
Frequency = (F
o
* 2
32
/Ref osc)
Where F
o
is the output frequency and Ref osc is the reference oscillator
frequency. If the AFG’s internal 42.94967296 MHz oscillator is used, the
equation simplifies to:
Frequency = (F
o
* 100)
Frequency is converted to the form:
(F
1
*2
24
+ F
2
*2
16
+ F
3
*2
8
+F
4
)/100
For example, to send 1kHz in four bytes (using the AFG internal oscillator):
Frequency = (1E3 * 100) = 100,000
= 00 01 86 A0
16
= 0 1 134 160
10
byte 1 byte 2 byte 3 byte 4
Arbitrary Waveform
Frequency
The maximum frequency of an arbitrary waveform using the AFG internal
oscillator is 10.48576 kHz (42.94967296E6/4096). Higher frequencies can
be achieved, however; the arbitrary waveform cannot contain frequency
components greater that 15 MHz. At 10.48576 kHz, each amplitude point is
output once. At lower frequencies, some or all points may be output more
than once. At higher frequencies, some points are skipped on each repetition.
244 HP E1340A Register-Based Programming Appendix C