Measurement-computing Serial488A Manuel d'utilisateur télécharger pdf (Page 38)

3.4

When the serial input buffer becomes empty, the

Serial488A

checks

the last characters sent to the IEEE bus device. If these were the IEEE bus

terminators and

Talk-Back on Terminator

is enabled, the IEEE bus

device is addressed to talk. Any data received by the

Serial488A

from the

bus device is sent to the serial host.

When the last IEEE bus terminator is detected from the IEEE device,

the

Serial488A

disables the device from sending additional information by

asserting Attention (ATN) on the bus.

If the IEEE device does not responded or finish transmission by the

time additional characters are received into the serial input buffer, the talk

sequence will be aborted to allow additional serial information to be sent to

the IEEE device.

The following is an example of how this feature can be used to

communicate with a single IEEE instrument. The program example is

written in Basic on an IBM PC or compatible and communicates with a

Keithley Model 196 DMM.

10 '

20 ' Example Program using Serial488A with

25 ' the Talk Back on Terminator Feature Enabled to

30 ' Communicate with a Keithley Model 196 DMM

40 '

50 ' Open Basic's serial communications port

60 OPEN "COM1: 9600,N,8,2" AS 1

70 ' Set the Model 196 DMM to the 30VDC range

80 PRINT #1,"F0R3X"; ' The ; suppresses terminators

90 ' Request 10 Readings from 196"

100 FOR N = 1 to 10

110 PRINT #1,"" ' Output terminator

120 LINE INPUT #1, A$ ' Get Reading from 196

130 PRINT A$ ' print it on the screen

140 NEXT N

150 END

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Measurement-computing Serial488A Manuel d'utilisateur Page 38