and interface hardware and software being used.
The differences occur primarily in the syntax used
to invoke the desired command, particularly
among different programming languages. Any
GPIB controller (i.e., a computer with a GPIB card)
should have available the messages defined in this
section. They may be identified differently in the
actual programming implementation.
DCL
The DEVICE CLEAR (DCL) command is used to
reset the internal GPIB functions of all devices on
the GPIB that respond to this command. The PCS
400 re-initializes itself the same as when it is going
through the power-up sequence.
GET
The GROUP EXECUTE TRIGGER (GET) is used to
synchronize the acquisition of data between several
instruments connected to the GPIB. When the PCS
400 receives a GET the current GPIB output reading
is latched until it is read over the bus. The display
output will continue to update.
GTL
The GO TO LOCAL (GTL) command places the PCS
400 into the LOCAL mode. This will allow the user
to change the engineering units, resolution, etc.
from the front panel. The PCS 400 does not respond
to the keypad while in the REMOTE mode.
IFC
The INTERFACE CLEAR (IFC) command halts all
current operations on the bus.
LLO
The PCS 400 always has LOCAL LOCKOUT (LLO)
enabled when the instrument is in the REMOTE
mode.
SDC
SELECTED DEVICE CLEAR (SDC) is similar in
function to DEVICE CLEAR (DCL) except that only
the device addressed to listen is reset.
SRQ
A SERVICE REQUEST (SRQ) is sent by the PCS 400
when it detects an error.
Serial Poll
A SERIAL POLL is a high level function of the GPIB
interface used to read the status byte of one par-
ticular device. Some GPIB interface manufacturers
provide this as an automatic function, reading the
most recent status byte from the instrument after
each read or write instruction. Others require the
user to specifically program the GPIB to do a
SERIAL POLL of a device.
A common use of the SERIAL POLL is in a program
module designed to respond to the service request
(SRQ) line on the GPIB. Many GPIB interface manu-
facturers provide a way to check the status of the
SRQ line. If it is asserted, some instrument on the
bus requires service. The service may involve sim-
ply acknowledging a change in instrument status,
completion of some internal function of the instru-
ment, or indicate the existence of an error. The
status byte returned by the serial poll will deter-
mine the required service and clear the SRQ. The
PCS 400 will always return a status byte of 00H
unless an error condition exists. If some other error
code is returned refer to table 4.2 for a listing of all
of the error codes and messages.
PCS 400 Command Set
Definitions
1. <> Optional information in the com-
mand.
2. • Delimiter required between adja-
cent elements in a command. A
space, comma or tab are valid de-
limiters.
3. unitno One or two digit number that desig-
nates the units of measure. See the
‘Measurement Units’ table in the Ap-
pendix.
4. value A floating point number that can
take the following format:
decimal_digit<decimal point>
<decimal_fraction><exponent_
part signed_integer_exponent>
Examples: 23, 23.45, 23., .2345e2,
.23E+2, .023E–1
5. digit A single decimal digit.
Example: 0, 1, 2 (single digit)
6. digits One or more decimal digits.
Example: 1, 01, 10, 66, 12345
7. sp Space. (32 decimal), (20 hex)
8. cr Carriage return. (13 decimal), (0D
hex)
9. lf Linefeed. (10 decimal), (0A hex)
10. EOI End Or Identify (End of transmis-
sion). When the ATN line is true, the
EOI line is used by the controller to
execute a parallel poll. When the
ATN line is false, the EOI line is used
by an active talker to indicate the
REMOTE OPERATION PCS 400
4-2 www.mensor.com
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