HP Car 3490A 3 - 87GENERAL.PURPOSEINTERFACEBUSI/O (0ption, the, the, sRo, and, for, nor, The, ..0, the, the, the, form, that, 030), _The, Data, data, been, DIOI, also, data

Model34904

REIUOTE

ENAELE

PROGRAI\,I

LINES

PROGRAM

EXECUTE

PROGRAM
l	t	t	l	t	l
r	t	l	l	l	l
l	r	r t		t	l l
349A.4-2936 II	T2 T3 T4 15 T6 T7

Tl - Remote Enable must be held LOW to permit remote programming. For reliable operation, T1 should occur first. lf Remote Enable goes HIGH, program capability reverts to front panel controls.

T2 - Selection of range and f unction programming. Input

SectionIII

3-89. The operatinginstructionscontained in this sec-

tion include addresscodesand addresscode selection, program codes, output format, and timing sequence information. The GPIB systemusesthe ASCII (Ameri-

can StandardCode for Information Interchange)eight- bit octal codein a parallelbit, serialcharacterform.

3-90.GPIBBusSignals.

3-91.For convenienceand brevity, eachbus signalline is identified by a mnemonic,which is an abbreviationof the signalname. Table 3-5 lists the signalsused on the GPIB bus. An H precedinga mnemonic indicates that the signalis HIGH true, L indicatesLOW is true.

Table3-5. GPIBSignalMnemonics.

lines are HIGH unless forced LOW at Remote lnput connector. T1 and T2 may be simultaneous.

T3 - Program Execute level must be LOW for a minimum of 5 ms. T2 and T3 may be simultaneous.

T4 - Program Flag initiates ourguard-to-inguard transfer of program information, Interval between T3 and T4 depends upon point in scan sequence at which T3 occurs.

M n e m o n i c

DAC

D A V

D r o ( 1 € )

EOP

M R E

R E N

R F D

sRo

SignalName

Data Accepred Data Valid

Data lnput/Output End Output

Multiple ResponseEnable Remote Enable

Ready For Data

ServiceRequest

T5 - Transfer of program information is complete. Exrernar Encodemay be applied.

T6 - Program lines may be returned to HIGH, if desired,at any time after Program Flag goes LOW. Any program line need not be returned to HIGH unlessrequired by a subsequent program change.

T7 -ProgramExecute must return to HIGH before a subsequent program change can be made.

Figure3-6. RemoteProgramSequence(Option 022).

will maintain all normal- and common.moderejection characteristicswith the Remote Control lines properly connected. Outguard ground is isolated from inguard common and from chassis(power line) groundand r-naybe floated up to 40 V abovechassis.

3 - 87GENERAL.PURPOSEINTERFACEBUSI/O (0ption

030).

3.-88_TheGeneralPurposeInterfaceBusI/O option for the Model 3490A Digital Voltmeter allows the instru_ ment to be controlled remotely and to output measure_ ment information to a digitalrecorder.It peimits remote programming of range, function, trigger mode, and Sample/Holdmode. Neither the poweiline switch nor the Ratio mode can be programmed remotely. The

output data includes measurementstatus, function, polarity, magnitude,and range,in the forrnat given in

Paragaph3-126.Severalinstiumentsmay be connected

in parallel to the samebus and controlied by a sinsle controlling insrrumenr. Controlling instruments thlat

may be used with the 34904 GpIB option include the

-hp9800 seriescalculatorsand the _hp_

Model 32604

\larked CardProgammer.

3-92.Data Lines DlOl through DlOg. All eight Data Input/Output lines are LOW true, as indicatedby the L

at the beginningof the mnemonic.(LOW= logical..1".) In the 3490A,DIO8 is alwaysHIGH, or logical..0".

3-93.Multiple ResponseEnable,MRE. Whenthe Multi_ ple ResponseEnableline is LOW, all units connectedto the bus must respondto the controllerand interpret the

data on lines DIOI through DIOT as an adäressor command.WhenMRE is HIGH, only the unit which has been addressedas the talker and the unit (or units) addressedas listener(s)may and arerequiredto respond 0n the DAV, DAC, and RFD lines.

'"'

3-94. HandshakeSignals.Threelines are usedfor what is called a "Handshaking" technique. The listener (or

listeners) set RFD to HIGH to indicate readinessto accept data. The RFD line is wire OR'dto all units on

the bus so that data will not be transmitted until the slowestlistener on the bus signalsthat it is ready for data.Whenall listenersareready(RFD goesHIGH), the talker puts the first characteron the dattlines, DIOI _g. Whenthe data is valid, the talker setsDAV to LOW. As

each listenerreceivesand has completedprocessingthis

data, it allowsits DAC output to go HIGH. This line is also wire OR'd to each unit, and the line does not actually go HIGH until all listenershave acceptedthe data. The talker may not changethe data on DIOI _g untilDAC goesHIGH.

3-95.RFD. Each listenermay set RFD HIGH as soon asit hascompletedand acknowledgedacceptanceof the previous data. This signalsto the talker that it mav transmitnew dataon the datalinesDIOI - g.

3-1