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RAM Size
Starting the
Waveform
Querying the AFG
Appendix C
The Frequency Register (bit 5) and RAM size (bits 1 - 0) bits are
ignored.
Direct DAC access - this mode sends waveform data to the DAC
directly from the Input Data Register (base + 0C
mode is set, the RAM bank, Frequency Register, and RAM size bits
are ignored. The frequency is set to DC, and the output remains at
the given voltage until the Input Data Register is written to again.
This mode is used to generate an arbitrary waveform whose
frequency and size (number of points) is limited by a controller's
speed and its amount of memory. This mode is set together with the
"Input Data Register" clock source (bits 5 -3 of byte 1).
Fast Frequency change - this mode is used to continuously change
the output signal frequency in order to make custom frequency
profiles. The AFG outputs a new frequency each time four
(frequency) bytes are written to the Parameter Register. This mode
uses the 4k RAM size. The Frequency Register and RAM size bits
are ignored.
The RAM size (bits 1 - 0 of byte 2) specifies whether one, two, or four
waveforms will comprise the output waveform. If the RAM size is 8k or
16k, the RAM bank (bits 7 - 6) is ignored.
When register-based programming, the waveform is output when byte 2 of
the output mode is processed by the AFG. If the "external burst" mode is
set, the waveform is output when an external trigger is received.
AFG parameters are queried by sending command opcode 13 followed by a
query opcode. The response to the query is returned to the Query Response
Register (base + 08
).
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The AFG parameters that can be queried include:
function
frequency (registers 1 and 2)
attenuation
offset
burst count
sweep rate
mode
Each time opcode 13 and a query opcode are sent one byte is returned. For
example, to query the frequency, opcode 13 must be sent four times (with a
different query code) to return the four bytes which set the frequency.
HP E1340A Register-Based Programming 251
). When this
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