Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 90)

II. SOFTWARE GUIDES - 8. Driver488/DRV 8H. Turbo C
Personal488 User’s Manual, Rev. 3.0 II-75
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:
ieeewt(“status\n”);
ieeerd(response);
printf(“%s\n”,response);
Subsequently, the printed response is similar to the following:
CS21 1 I000 000 T0 C0 P0 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 that 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
F0R0X command
line below sets the 195 to read DC volts with automatic range selection:
ieeewt(“output 16;F0R0X\n”);
The OUTPUT command takes a bus device address ( 16 in this case) and data ( F0R0X ) and sends the data
to the specified device. The address can be just a primary address, such as 12 , or 05 , or it can include
a secondary address: 1201 . Note that both the primary address and, if present, the secondary address
are two-digit decimal numbers. A leading zero must be used, if necessary to make a two-digit address.
Taking Readings
Once we have set the 195’s operating mode, we can take a reading and display it:
float voltage;
ieeewt(“enter 16\n”);
ieeescnf(“%*4s%e”,&voltage);
printf(“The read value is %g\n”,voltage);
The ENTER command takes a bus address (with an optional secondary address) and configures that bus
device so that it is able to send data (addressed to talk). No data is actually transferred, however, until
the
IEEESCNF statement requests the result from Driver488/DRV at which time data is transferred to
the program into the variable voltage . A typical reading from a 195 might be NDCV+1.23456E-2 ,
consisting of a four character prefix followed by a floating point value. The format passed to
IEEESCNF causes it to skip the four character prefix ( %*4s ) and then convert the remaining string into
the float variable voltage .
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”.