Rotek 811AE - Ending a Test Routine; Precautions

48
The Energy Delivered data may be read after the 811A or 811AE has completed counting the
desired number of pulses from the energy meter under test. The Data Available bit of the status byte
will be asserted. The following routine illustrates the procedure which should be followed to read the
energy delivered data.
'Begin Counting pulses
CALL SEND(12, "Q", Status%)
'Loop while the 811A/811AE is counting
DO WHILE (Poll% AND 16) = 1
CALL SPOLL(12, Poll%, Status%)
LOOP
'Loop until the Data Available bit of the status Byte is set
DO WHILE (Poll% AND 2) = 0
CALL SPOLL(12, Poll%, Status%)
LOOP
'Read the Energy Delivered data
Result$ = SPACE$(80)
CALL ENTER(Result$, Length%, 12, Status%)
Result$ = LEFT$(Result$, Length%)
In this routine the timing bit of the status byte is interrogated until it has been reset and then the Data
Available bit is asserted as there is a finite period of time between the two events. The structure of
the transmitted word is given in Table 5-4.
5.6.6 Ending a Test Routine
In the interest of safety the Calibrator should be returned to a well defined, safe state after
the task it has been programmed for has been completed. This can most easily be done by issuing
the Select Device Clear message from the controller. It may also be wise to check the status byte
and confirm that the Standby state was achieved.
5.6.7 Precautions
In general it is always good practice to interrogate the Busy and Timing status bits of the
status byte before or immediately after sending data to assure that the Series 800 received the
correct information and is not operating on old data. If the input data rate is faster the Calibrator can
allow the input buffer will become full all buffer data is cleared and Standby is asserted. This could
happen if the counting mode is in operation and data is continuously sent to the Calibrator
(811A/811AE only). This situation could also occur during any other mode where the µP is
performing a previously requested task and is not available for handling new data.
No attempt is made here to examine the diverse intricacies of programming since it is far
beyond the scope of this manual. For detailed information on the operation and syntax of the IEEE-
488 Bus interface controller the reader is referred to the instruction manual for the controller being
used.