Measurement Computing Serial488A - Manual (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