External Time Base

Establishes a hardware time-base for the model using the EXT_INT line of the Q8 data acquisition system.

Library

qctools

Description

The External Time Base block for the Q8 series of I/O cards provides a mechanism for using an external signal as a time-base for the real-time code. This block is typically used to synchronize multiple computers or to synchronize the real-time code with an external periodic event, such as a microcontroller clock or motor crankshaft. To synchronize multiple computers, use a Counter Time Base block on the "master" with the "Enable external output" option checked and use an External Time Base block on all the "slaves". Connect the CNTR_OUT or WATCHDOG output (according to the Counter Time Base clock source) of the master to the EXT_INT lines of the slaves.

	Note that Time Base 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.

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 an interrupt is triggered on the falling edge of the EXT_INT line. Otherwise it is triggered on the rising edge. The EXT_INT line has a pullup resistor to bring it high when the input is unconnected. Hence, this option is normally unchecked