External Interrupt

Asynchronously invokes the appropriate function-call subsystem when an external interrupt of the Q8 data acquisition system occurs.

Library

qctools

Description

The External Interrupt block for the Q8 series of I/O cards provides a mechanism for handling asynchronous external interrupts on the EXT_INT line. Attaching a function-call subsystem to an output causes the function-call subsystem to be executed as soon as the external interrupt occurs. The code executes asychronously from the rest of the model. The timing of its execution is not governed by the sampling period of the system.

	Note that the Asynchronous Interrupt blocks may only be used in Windows if the Q8 Windows driver has been converted to an RTX driver using Convert To RTX in the RTX Properties control panel. One of the Time Base blocks is also required in the model for these blocks to be used.

Block Outputs

EXTINT

The function-call subsystem attached to this output will execute when a rising or falling edge occurs on the EXT_INT line. The "EXT_INT polarity" option selects the edge on which to invoke the function-call subsystem.

Parameters and Dialog Box

Board Number

The board number of the I/O card. If there is only one Q8 board in your system, then the board number should be zero. The second Q8 board in your system is board number 1, etc.

EXT_INT Polarity

Polarity of the EXT_INT input. If this option is not checked then a falling edge on the EXT_INT input triggers the execution of the function-call subsystem. Otherwise a rising edge triggers its execution. The EXT_INT line has a pullup resistor to bring it high when the input is unconnected. Hence, this option is normally unchecked by default.

EXT_INT Acts as Watchdog

If this option is checked then a rising or falling edge on the EXT_INT input causes the analog outputs to be reset to zero and all the digital lines to be pulled high. This "watchdog" operation is performed in hardware. No software intervention is required. This feature is particularly useful for connecting limit switches and emergency stop buttons to the system. The active edge is determined by the EXT_INT Polarity parameter.