Vmebus Interrupt Configuration; Interrupt Request Line Selection; Interrupt Priority Code; Figure 3-4. Vmebus Interrupt Line Selection - National Instruments Corporation GPIB-1014P User Manual

Section Three Configuration and Installation

VMEbus Interrupt Configuration

The GPIB-1014P contains circuitry that permits it to request service by driving one of the VMEbus
interrupt request lines. The GPIB-1014P responds to an interrupt acknowledge cycle of correct
priority by providing an 8-bit vector (status byte) that is used to locate the appropriate interrupt
service routine. The following paragraphs explain the actions that must be performed to configure
the interrupt request line, the interrupt priority, and the status/ID byte or interrupt vector.

Interrupt Request Line Selection

The VMEbus provides seven interrupt request lines IRQ1* to IRQ7*. The GPIB-1014P can be
configured to drive any one of these seven lines. The jumper shown in Figure 3-4 is used to
connect the interrupt request from the GPIB-1014P to one of the VMEbus interrupt request lines.
The jumper is placed on the pins that correspond to the desired interrupt request line.
Note: The interrupt priority code must be set to correspond to the interrupt request line.
Figure 3-4a shows the jumper configured to select interrupt request line IRQ2*, while Figure 3-4b
shows the configuration for selecting IRQ4*. The default setting for the GPIB-1014P is IRQ2*.
1 7 1 7
IRQ IRQ
a. Select Interrupt Request Line Configured b. Select Interrupt Request Line Configured
to IRQ2* to IRQ4*
(Default setting)

Figure 3-4. VMEbus Interrupt Line Selection

Note: An asterisk implies that the signal is active low.

Interrupt Priority Code

The interrupt priority code is used to identify an interrupt acknowledge cycle intended for the GPIB-
1014P. Three bits, I1 through I3, represent the interrupt priority code of the GPIB-1014P. The
encoded value of these three bits must correspond to the interrupt request line used (1 through 7) by
the board, I1 is the least significant bit. Three switches located at U28 set these bits. Press the side
labeled 0 to select a logical zero for the corresponding address bit. Press the side labeled 1 to select
a logical one. Figure 3-5a shows the switch configuration for using IRQ2* while Figure 3-5b
shows the switch configuration for using IRQ4*. The default setting for the GPIB-1014P is
IRQ2*.
© National Instruments Corporation 3-5 GPIB-1014P User Manual