Chapter 8 Interrupt Control©National Instruments Corporation8-5DAQ-STC Technical Reference ManualUse the following function to enable the use of an external secondary interrupt condition onpins IRQ_IN<0..1>.Function MSC_Pass_Through_Second_Irq{switch (pass through secondary interrupt){case 0:Pass_Thru_0_Second_Irq_Enable = 0 (disabled) or 1 (enabled);break;case 1:Pass_Thru_1_Second_Irq_Enable = 0 (disabled) or 1 (enabled);break;}}Note You should set Pass_Through_i_Interrupt_Enable to 1 after selecting theinterrupt polarity.8.4.2 Interrupt HandlingUp to 18 events occurring within the DAQ-STC and up to two events occurring outside theDAQ-STC can cause the DAQ-STC to assert an interrupt. This section presents aprogramming sequence you can use to determine which of the many conditions caused theinterrupt. You will find suggestions for interrupt-servicing programs in the other chapters ofthis manual.Keep a record of interrupts that you enable so that you can determine which condition causedthe interrupt. You should have software copies of all the relevant write-only registers. It isassumed that you want to service every condition that can cause an interrupt.For instructions on programming the physical interrupt interface circuitry, see section 8.4.1,Programming the Interrupt Interface. For information on how your system uses theDAQ-STC interrupts, consult your hardware and computer manuals.Conditions that can cause interrupts are divided into group A and group B. Group A containsconditions generated by or related to analog input control and timing circuitry,general-purpose counter 0, and pass-through interrupt 0. Group B contains conditionsgenerated by or related to analog output control and timing circuitry, general-purpose counter1, and pass-through interrupt 1. You can enable the two groups independently, and you canchoose any of the eight interrupt levels for each group, or the two groups can share an interruptlevel.The following sections present the functions that should be executed when an appropriateinterrupt is asserted.
