Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 100)

II. SOFTWARE GUIDES - 8. Driver488/DRV 8I. Turbo Pascal
Personal488 User’s Manual, Rev. 3.0 II-85
Next, we can enable SEQUENCE - NO DATA AVAILABLE error detection by setting the FILL mode to
ERROR :
Writeln(IeeeOut,’FILL ERROR’);
The IOCTL , RESET , and FILL ERROR statements are also included in the IEEEIO unit initialization
code.
Once everything is reset, we can test the communications and read the Driver488/DRV revision number
with the
HELLO command:
VAR Response: STRING;
Writeln(IeeeOut,’HELLO’);
Readln(IeeeIn,Response);
Writeln(Response);
First we Writeln the HELLO command to IeeeOut , then we Readln the response from IeeeIn into
the character variable Response . Finally we display the response with a Writeln to the screen.
Because Turbo Pascal cannot both Writeln and Readln from the same text file, we use two different
files to communicate with Driver488/DRV. Writeln must reference the file opened for output (in
these examples, IeeeOut ) and Readln must reference the file opened for input ( IeeeIn ). Attempting
to communicate with the wrong file (such as Writeln(IeeeIn_) ) results in an error.
It is not necessary to perform the HELLO command, but it is included here as a simple example of
normal communication with Driver488/DRV. Its response is the revision identification of the
Driver488/DRV software:
Driver488 Revision X.X ©199X IOtech, Inc.
We can also interrogate Driver488/DRV for its status:
Writeln(IeeeOut,’STATUS’);
Readln(IeeeIn,Response);
Writeln(Response);
Subsequently, the printed response is similar to the following:
CS21 1 I000 000 T0 C0 P0 OK
The following indicators describe each component of the Driver488/DRV status:
Indicator Driver488/DRV Status
C It is in the Controller state.
S It is the System Controller.
21 The value of its IEEE 488 bus address.
1 An Address Change has occurred.
I It is idle (neither a talker nor a listener).
0 There is no ByteIn available.
0 It is not ready to send a ByteOut .
0 Service Request ( SRQ ) is not asserted.
000 There is no outstanding error.
T0 It has not received a bus device TRIGGER command (only applicable in the Peripheral
mode).
C0 It has not received a CLEAR command (only applicable in the Peripheral mode).
P0 No CONTINUE transfer is in progress.
OK The error message is “OK”.
Configuration of the 195 DMM
Once the system is initialized we are ready to start issuing bus commands. The IEEE 488 bus has
already been cleared by the Interface Clear (
IFC ) sent by the RESET command, so we know all bus
devices are waiting for the controller to take some action. To control an IEEE 488 bus device, we
OUTPUT an appropriate device-dependent command to that device. For example, the command F0R0X
sets the 195 to read DC volts with automatic range selection: