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Table Of Contents
Part 5: IEEE 488.2 Programming Reference
Parallel Polling
Like serial polling, this is only useful when several oscilloscopes are connected. The controller
simultaneously reads the Individual STatus bit (IST) of all oscilloscopes to determine which one needs
service. This method allows up to eight different oscilloscopes to be polled at the same time.
When a parallel poll is initiated, each oscilloscope returns a status bit over one of the DIO data lines.
Devices may respond either individually, using a separate DIO line, or collectively on a single data line.
Data-line assignments are made by the controller using a Parallel Poll Configure (PPC) sequence.
The following example uses the INE 1 command to enable the event "new signal acquired" in the INR for
reporting to the INB bit of the status byte STB. The PaRallel poll Enable register (PRE) determines which
events are summarized in the IST status bit. The command *PRE 1 enables the INB bit (when first set
itself) to set the IST bit. Once parallel polling is established, the parallel-poll status is examined until a
change on data bus line DIO2 takes place.
Example: Parallel Polling, Stage 1
Enable the INE and PRE registers; configure the controller for parallel poll; instruct the oscilloscope to
respond on data line 2 (DIO2) using these commands:
CMD1$ = DSOListenPCTalk$ 'As defined earlier
CALL IBCMD (BRD0%, CMD1$)
CMD$ = "INE 1;*PRE 1"
CALL IBWRT (BRD0%, CMD$)
PPE$ = Chr$ (&H5) 'GPIB Parallel Poll Enable
MSA9$ = Chr$ (&H69) 'GPIB Secondary Address 9
CMD4$ = PPE$ + MSA9$ + UnListen$
CALL IBCMD (BRD0%, CMD4$)
Example: Parallel Polling, Stage 2
Parallel poll the oscilloscope until DIO2 is set using these commands:
Do
CALL IBRPP (BRD0%, PPR%)
Loop Until (PPR% AND &H2) = 2
Example: Parallel Polling, Stage 3
Disable parallel polling (hex 15) and clear the parallel poll register using these commands:
PPU$ = Chr$ (&H15) 'GPIB Parallel Poll Unconfigure
CALL IBCMD (BRD0%, PPU$)
CALL IBCMD (BRD0%, CMD1$) 'As defined earlier
CMD$ = "*PRE 0" : CALL IBWRT(BRD0%,CMD$):
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