Tektronix FCA3000 Programmer's Manual page 143

Using the *WAI Command
Using the *OPC Command
FCA3000, FCA3100, MCA3000 Series Programmer Manual
TRIGGER:COUNT 1000; :ARM COUNT 1
DISPLAY:ENABLE ON
FORMAT ASCII; :TINFORMATION OFF
/** Start measurement**/
INITIATE
/** Read results **/
FETCH:ARRAY? 1000
Measurements require extended processing time. They may not finish before the
controller attempts to read the results. To be sure the instrument completes the
measurements before the controller reads them, you can synchronize the program.
You can use three commands to synchronize the operation of the instrument with
your application program: *WAI, *OPC, and *OPC?
The *WAI command forces completion of previous commands that generate
an OPC message. No commands after the *WAI are processed before the OPC
message(s) are generated
The same command sequence using the *WAI command for synchronization
looks like this:
/** Set up for period measurement **/
FUNCTION "PERIOD 1"
INPUT:LEVEL 0; :AUTO OFF; :COUPLING DC
TRIGGER:COUNT 1000; :ARM COUNT 1
DISPLAY:ENABLE ON
FORMAT ASCII; :TINFORMATION OFF
/** Start measurement**/
INITIATE
/* Wait until the measurements are complete before
reading them*/
*/
*WAI
/** Read results **/
FETCH:ARRAY? 1000
The controller can continue to write commands to the input buffer of the
instrument, but the commands will not be processed by the instrument until all
in-process OPC operations are complete. If the input buffer becomes full, the
controller is unable to write commands to the buffer. This can cause a time-out.
If the corresponding status registers are enabled, the *OPC command sets the
OPC bit in the Standard Event Status Register (SESR) when an operation is
complete. You achieve synchronization by using this command with either a
serial poll or service request handler.
Status and Events
3-7