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C-10
DDC Emulation Commands
klqb
F) Since the Model 487 DDC Mode allows for one saved user setup to be the power-
on default, the *SAV 0 location is used for the saved DDC defaults. Therefore,
changing the instrument language to DDC will clear out the *SAV 0 location and
load it with the DDC factory defaults. A setup saved using the DDC mode L1 com-
mand will be saved into this location. Likewise, changing the Model 6487 language
from DDC mode to SCPI will return the SYST:PRESet factory defaults into the
*SAV 0 setup location, overwriting the setup that had been stored with the DDC
mode L1 command.
G) Calibration can be performed only with SCPI calibration commands. See
Appendix
F.
H) Multiple SRQ conditions can be enabled by adding up M command values. For
example, M33 enables SRQ both on reading done and on error.
I)
The DDC errors do not map one-to-one with SCPI errors. There are two SCPI
errors that cover all of the 6487 Error Events (EE). This will be fairly equivalent
to using the M16 DDC command. After getting an SRQ on an Error Event, to
clear the event, read the Standard Event Register (*ESR?, then talk the instru-
ment). There may also be an Error Available event set in the status byte (serial
poll).
J)
Buffer operating notes:
a.
The 6487 does not support a continuous wrap-around buffer. Therefore,
the N0 command will simply stop storage and clear the buffer.
b.
Nx (x=1-512) will arm the buffer and storage will commence at the first
trigger. A key difference between the 487 and the 6487 is that pressing
the LOCAL key on a 6487 puts the unit back into continuous trigger
mode, so storage will start immediately. On the 487, however, you must
press LOCAL followed by a separate press of the TRIGGER key. If all
triggering is handled over the GPIB, this difference will not matter in
actual practice. Although the 6487 buffer is capable of storing 3000 read-
ings, in DDC mode the limit is the same 512 readings as the 487.
K) The digital filter is always a 4-point moving average type and cannot be changed in
DDC mode.
L) See ARM and TRIGger subsystems in
M) The 487 does not allow R8 or R9, since its highest measurement range is R7,
which is the 2mA range. The 6487 accepts R8 and R9, both of which select the
20mA range. Whether R8 or R9 is sent, an '8' will show up in the range position
of the U0 response string. R10 is still used to disable auto range and remain on
the present range as in the 487.
N) SCPI PMT (Program Message Terminator) is always LF + EOI.
DDC timing is not guaranteed to match the timing of the original instrument
(487) being emulated.
Model 6487 Reference Manual
Section
14.
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